Merge branch 'development' of https://github.com/0xProject/0x-monorepo into website/feature/react-16

38 files changed, 2888 insertions, 775 deletions

diff --git a/packages/contracts/compiler.json b/packages/contracts/compiler.json
index 16524231c..f66114e87 100644
--- a/packages/contracts/compiler.json
+++ b/packages/contracts/compiler.json
@@ -40,6 +40,7 @@
         "MultiSigWallet",
         "MultiSigWalletWithTimeLock",
         "OrderValidator",
+        "ReentrantERC20Token",
         "TestAssetProxyOwner",
         "TestAssetProxyDispatcher",
         "TestConstants",
@@ -47,6 +48,7 @@
         "TestLibs",
         "TestExchangeInternals",
         "TestSignatureValidator",
+        "TestStaticCallReceiver",
         "TokenRegistry",
         "Validator",
         "Wallet",
diff --git a/packages/contracts/package.json b/packages/contracts/package.json
index 10ab09767..5d2f290ac 100644
--- a/packages/contracts/package.json
+++ b/packages/contracts/package.json
@@ -1,7 +1,7 @@
 {
     "private": true,
     "name": "contracts",
-    "version": "2.1.41",
+    "version": "2.1.42",
     "engines": {
         "node": ">=6.12"
     },
@@ -33,7 +33,7 @@
         "lint-contracts": "solhint src/2.0.0/**/**/**/**/*.sol"
     },
     "config": {
-        "abis": "../migrations/artifacts/2.0.0/@(AssetProxyOwner|DummyERC20Token|DummyERC721Receiver|DummyERC721Token|DummyNoReturnERC20Token|ERC20Proxy|ERC721Proxy|Forwarder|Exchange|ExchangeWrapper|IAssetData|IAssetProxy|InvalidERC721Receiver|MixinAuthorizable|MultiSigWallet|MultiSigWalletWithTimeLock|OrderValidator|TestAssetProxyOwner|TestAssetProxyDispatcher|TestConstants|TestExchangeInternals|TestLibBytes|TestLibs|TestSignatureValidator|Validator|Wallet|TokenRegistry|Whitelist|WETH9|ZRXToken).json"
+        "abis": "../migrations/artifacts/2.0.0/@(AssetProxyOwner|DummyERC20Token|DummyERC721Receiver|DummyERC721Token|DummyNoReturnERC20Token|ERC20Proxy|ERC721Proxy|Forwarder|Exchange|ExchangeWrapper|IAssetData|IAssetProxy|InvalidERC721Receiver|MixinAuthorizable|MultiSigWallet|MultiSigWalletWithTimeLock|OrderValidator|ReentrantERC20Token|TestAssetProxyOwner|TestAssetProxyDispatcher|TestConstants|TestExchangeInternals|TestLibBytes|TestLibs|TestSignatureValidator|TestStaticCallReceiver|Validator|Wallet|TokenRegistry|Whitelist|WETH9|ZRXToken).json"
     },
     "repository": {
         "type": "git",
@@ -46,11 +46,11 @@
     },
     "homepage": "https://github.com/0xProject/0x-monorepo/packages/contracts/README.md",
     "devDependencies": {
-        "@0xproject/abi-gen": "^1.0.6",
-        "@0xproject/dev-utils": "^1.0.5",
-        "@0xproject/sol-compiler": "^1.1.0",
-        "@0xproject/sol-cov": "^2.1.0",
-        "@0xproject/subproviders": "^2.0.0",
+        "@0xproject/abi-gen": "^1.0.7",
+        "@0xproject/dev-utils": "^1.0.6",
+        "@0xproject/sol-compiler": "^1.1.1",
+        "@0xproject/sol-cov": "^2.1.1",
+        "@0xproject/subproviders": "^2.0.1",
         "@0xproject/tslint-config": "^1.0.6",
         "@types/bn.js": "^4.11.0",
         "@types/ethereumjs-abi": "^0.6.0",
@@ -73,12 +73,12 @@
         "yargs": "^10.0.3"
     },
     "dependencies": {
-        "@0xproject/base-contract": "^2.0.0",
-        "@0xproject/order-utils": "^1.0.1-rc.4",
-        "@0xproject/types": "^1.0.1-rc.5",
+        "@0xproject/base-contract": "^2.0.1",
+        "@0xproject/order-utils": "^1.0.1-rc.6",
+        "@0xproject/types": "^1.0.1-rc.6",
         "@0xproject/typescript-typings": "^1.0.5",
-        "@0xproject/utils": "^1.0.6",
-        "@0xproject/web3-wrapper": "^2.0.0",
+        "@0xproject/utils": "^1.0.7",
+        "@0xproject/web3-wrapper": "^2.0.1",
         "@types/js-combinatorics": "^0.5.29",
         "bn.js": "^4.11.8",
         "ethereum-types": "^1.0.5",
diff --git a/packages/contracts/src/2.0.0/examples/Whitelist/Whitelist.sol b/packages/contracts/src/2.0.0/examples/Whitelist/Whitelist.sol
index 60cac26ea..e4e25038c 100644
--- a/packages/contracts/src/2.0.0/examples/Whitelist/Whitelist.sol
+++ b/packages/contracts/src/2.0.0/examples/Whitelist/Whitelist.sol
@@ -37,7 +37,7 @@ contract Whitelist is
     bytes internal TX_ORIGIN_SIGNATURE;
     // solhint-enable var-name-mixedcase
 
-    byte constant internal VALIDATOR_SIGNATURE_BYTE = "\x06";
+    byte constant internal VALIDATOR_SIGNATURE_BYTE = "\x05";
 
     constructor (address _exchange)
         public
diff --git a/packages/contracts/src/2.0.0/extensions/Forwarder/MixinExchangeWrapper.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinExchangeWrapper.sol
index 218713d3c..9e816716c 100644
--- a/packages/contracts/src/2.0.0/extensions/Forwarder/MixinExchangeWrapper.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinExchangeWrapper.sol
@@ -69,20 +69,14 @@ contract MixinExchangeWrapper is
                 fillOrderCalldata,                  // write output over input
                 128                                 // output size is 128 bytes
             )
-            switch success
-            case 0 {
-                mstore(fillResults, 0)
-                mstore(add(fillResults, 32), 0)
-                mstore(add(fillResults, 64), 0)
-                mstore(add(fillResults, 96), 0)
-            }
-            case 1 {
+            if success {
                 mstore(fillResults, mload(fillOrderCalldata))
                 mstore(add(fillResults, 32), mload(add(fillOrderCalldata, 32)))
                 mstore(add(fillResults, 64), mload(add(fillOrderCalldata, 64)))
                 mstore(add(fillResults, 96), mload(add(fillOrderCalldata, 96)))
             }
         }
+        // fillResults values will be 0 by default if call was unsuccessful
         return fillResults;
     }
 
@@ -163,7 +157,7 @@ contract MixinExchangeWrapper is
 
             // Convert the remaining amount of makerAsset to buy into remaining amount
             // of takerAsset to sell, assuming entire amount can be sold in the current order
-            uint256 remainingTakerAssetFillAmount = getPartialAmount(
+            uint256 remainingTakerAssetFillAmount = getPartialAmountFloor(
                 orders[i].takerAssetAmount,
                 orders[i].makerAssetAmount,
                 remainingMakerAssetFillAmount
@@ -231,7 +225,7 @@ contract MixinExchangeWrapper is
 
             // Convert the remaining amount of ZRX to buy into remaining amount
             // of WETH to sell, assuming entire amount can be sold in the current order.
-            uint256 remainingWethSellAmount = getPartialAmount(
+            uint256 remainingWethSellAmount = getPartialAmountFloor(
                 orders[i].takerAssetAmount,
                 safeSub(orders[i].makerAssetAmount, orders[i].takerFee),  // our exchange rate after fees 
                 remainingZrxBuyAmount
diff --git a/packages/contracts/src/2.0.0/extensions/Forwarder/MixinForwarderCore.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinForwarderCore.sol
index 42cec4d36..14f191879 100644
--- a/packages/contracts/src/2.0.0/extensions/Forwarder/MixinForwarderCore.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinForwarderCore.sol
@@ -87,7 +87,7 @@ contract MixinForwarderCore is
         uint256 makerAssetAmountPurchased;
         if (orders[0].makerAssetData.equals(ZRX_ASSET_DATA)) {
             // Calculate amount of WETH that won't be spent on ETH fees.
-            wethSellAmount = getPartialAmount(
+            wethSellAmount = getPartialAmountFloor(
                 PERCENTAGE_DENOMINATOR,
                 safeAdd(PERCENTAGE_DENOMINATOR, feePercentage),
                 msg.value
@@ -103,7 +103,7 @@ contract MixinForwarderCore is
             makerAssetAmountPurchased = safeSub(orderFillResults.makerAssetFilledAmount, orderFillResults.takerFeePaid);
         } else {
             // 5% of WETH is reserved for filling feeOrders and paying feeRecipient.
-            wethSellAmount = getPartialAmount(
+            wethSellAmount = getPartialAmountFloor(
                 MAX_WETH_FILL_PERCENTAGE,
                 PERCENTAGE_DENOMINATOR,
                 msg.value
diff --git a/packages/contracts/src/2.0.0/extensions/Forwarder/MixinWeth.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinWeth.sol
index 93e85e599..5863b522d 100644
--- a/packages/contracts/src/2.0.0/extensions/Forwarder/MixinWeth.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinWeth.sol
@@ -82,7 +82,7 @@ contract MixinWeth is
         uint256 wethRemaining = safeSub(msg.value, wethSold);
 
         // Calculate ETH fee to pay to feeRecipient.
-        uint256 ethFee = getPartialAmount(
+        uint256 ethFee = getPartialAmountFloor(
             feePercentage,
             PERCENTAGE_DENOMINATOR,
             wethSoldExcludingFeeOrders
diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC20Proxy.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC20Proxy.sol
index b5cec6b64..004c3892d 100644
--- a/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC20Proxy.sol
+++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC20Proxy.sol
@@ -118,6 +118,9 @@ contract ERC20Proxy is
                 mstore(96, 0)
                 revert(0, 100)
             }
+
+            // Revert if undefined function is called
+            revert(0, 0)
         }
     }
 
diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC721Proxy.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC721Proxy.sol
index 6a70c9f60..9d0bc0f74 100644
--- a/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC721Proxy.sol
+++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC721Proxy.sol
@@ -152,6 +152,9 @@ contract ERC721Proxy is
                 mstore(96, 0)
                 revert(0, 100)
             }
+
+            // Revert if undefined function is called
+            revert(0, 0)
         }
     }
 
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/MixinAssetProxyDispatcher.sol b/packages/contracts/src/2.0.0/protocol/Exchange/MixinAssetProxyDispatcher.sol
index e9f882194..80475e6e3 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/MixinAssetProxyDispatcher.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/MixinAssetProxyDispatcher.sol
@@ -83,7 +83,7 @@ contract MixinAssetProxyDispatcher is
         internal
     {
         // Do nothing if no amount should be transferred.
-        if (amount > 0) {
+        if (amount > 0 && from != to) {
             // Ensure assetData length is valid
             require(
                 assetData.length > 3,
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/MixinExchangeCore.sol b/packages/contracts/src/2.0.0/protocol/Exchange/MixinExchangeCore.sol
index ab5c6e507..ff908917d 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/MixinExchangeCore.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/MixinExchangeCore.sol
@@ -19,6 +19,7 @@
 pragma solidity 0.4.24;
 pragma experimental ABIEncoderV2;
 
+import "../../utils/ReentrancyGuard/ReentrancyGuard.sol";
 import "./libs/LibConstants.sol";
 import "./libs/LibFillResults.sol";
 import "./libs/LibOrder.sol";
@@ -30,6 +31,7 @@ import "./mixins/MAssetProxyDispatcher.sol";
 
 
 contract MixinExchangeCore is
+    ReentrancyGuard,
     LibConstants,
     LibMath,
     LibOrder,
@@ -54,6 +56,7 @@ contract MixinExchangeCore is
     /// @param targetOrderEpoch Orders created with a salt less or equal to this value will be cancelled.
     function cancelOrdersUpTo(uint256 targetOrderEpoch)
         external
+        nonReentrant
     {
         address makerAddress = getCurrentContextAddress();
         // If this function is called via `executeTransaction`, we only update the orderEpoch for the makerAddress/msg.sender combination.
@@ -86,43 +89,14 @@ contract MixinExchangeCore is
         bytes memory signature
     )
         public
+        nonReentrant
         returns (FillResults memory fillResults)
     {
-        // Fetch order info
-        OrderInfo memory orderInfo = getOrderInfo(order);
-
-        // Fetch taker address
-        address takerAddress = getCurrentContextAddress();
-
-        // Get amount of takerAsset to fill
-        uint256 remainingTakerAssetAmount = safeSub(order.takerAssetAmount, orderInfo.orderTakerAssetFilledAmount);
-        uint256 takerAssetFilledAmount = min256(takerAssetFillAmount, remainingTakerAssetAmount);
-
-        // Validate context
-        assertValidFill(
+        fillResults = fillOrderInternal(
             order,
-            orderInfo,
-            takerAddress,
             takerAssetFillAmount,
-            takerAssetFilledAmount,
             signature
         );
-
-        // Compute proportional fill amounts
-        fillResults = calculateFillResults(order, takerAssetFilledAmount);
-
-        // Update exchange internal state
-        updateFilledState(
-            order,
-            takerAddress,
-            orderInfo.orderHash,
-            orderInfo.orderTakerAssetFilledAmount,
-            fillResults
-        );
-    
-        // Settle order
-        settleOrder(order, takerAddress, fillResults);
-
         return fillResults;
     }
 
@@ -131,6 +105,7 @@ contract MixinExchangeCore is
     /// @param order Order to cancel. Order must be OrderStatus.FILLABLE.
     function cancelOrder(Order memory order)
         public
+        nonReentrant
     {
         // Fetch current order status
         OrderInfo memory orderInfo = getOrderInfo(order);
@@ -203,6 +178,64 @@ contract MixinExchangeCore is
         return orderInfo;
     }
 
+    /// @dev Fills the input order.
+    /// @param order Order struct containing order specifications.
+    /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
+    /// @param signature Proof that order has been created by maker.
+    /// @return Amounts filled and fees paid by maker and taker.
+    function fillOrderInternal(
+        Order memory order,
+        uint256 takerAssetFillAmount,
+        bytes memory signature
+    )
+        internal
+        returns (FillResults memory fillResults)
+    {
+        // Fetch order info
+        OrderInfo memory orderInfo = getOrderInfo(order);
+
+        // Fetch taker address
+        address takerAddress = getCurrentContextAddress();
+        
+        // Assert that the order is fillable by taker
+        assertFillableOrder(
+            order,
+            orderInfo,
+            takerAddress,
+            signature
+        );
+        
+        // Get amount of takerAsset to fill
+        uint256 remainingTakerAssetAmount = safeSub(order.takerAssetAmount, orderInfo.orderTakerAssetFilledAmount);
+        uint256 takerAssetFilledAmount = min256(takerAssetFillAmount, remainingTakerAssetAmount);
+
+        // Validate context
+        assertValidFill(
+            order,
+            orderInfo,
+            takerAssetFillAmount,
+            takerAssetFilledAmount,
+            fillResults.makerAssetFilledAmount
+        );
+
+        // Compute proportional fill amounts
+        fillResults = calculateFillResults(order, takerAssetFilledAmount);
+
+        // Update exchange internal state
+        updateFilledState(
+            order,
+            takerAddress,
+            orderInfo.orderHash,
+            orderInfo.orderTakerAssetFilledAmount,
+            fillResults
+        );
+    
+        // Settle order
+        settleOrder(order, takerAddress, fillResults);
+
+        return fillResults;
+    }
+
     /// @dev Updates state with results of a fill order.
     /// @param order that was filled.
     /// @param takerAddress Address of taker who filled the order.
@@ -259,20 +292,16 @@ contract MixinExchangeCore is
             order.takerAssetData
         );
     }
-
+    
     /// @dev Validates context for fillOrder. Succeeds or throws.
     /// @param order to be filled.
     /// @param orderInfo OrderStatus, orderHash, and amount already filled of order.
     /// @param takerAddress Address of order taker.
-    /// @param takerAssetFillAmount Desired amount of order to fill by taker.
-    /// @param takerAssetFilledAmount Amount of takerAsset that will be filled.
     /// @param signature Proof that the orders was created by its maker.
-    function assertValidFill(
+    function assertFillableOrder(
         Order memory order,
         OrderInfo memory orderInfo,
         address takerAddress,
-        uint256 takerAssetFillAmount,
-        uint256 takerAssetFilledAmount,
         bytes memory signature
     )
         internal
@@ -283,13 +312,7 @@ contract MixinExchangeCore is
             orderInfo.orderStatus == uint8(OrderStatus.FILLABLE),
             "ORDER_UNFILLABLE"
         );
-
-        // Revert if fill amount is invalid
-        require(
-            takerAssetFillAmount != 0,
-            "INVALID_TAKER_AMOUNT"
-        );
-
+        
         // Validate sender is allowed to fill this order
         if (order.senderAddress != address(0)) {
             require(
@@ -297,7 +320,7 @@ contract MixinExchangeCore is
                 "INVALID_SENDER"
             );
         }
-
+        
         // Validate taker is allowed to fill this order
         if (order.takerAddress != address(0)) {
             require(
@@ -305,7 +328,7 @@ contract MixinExchangeCore is
                 "INVALID_TAKER"
             );
         }
-
+        
         // Validate Maker signature (check only if first time seen)
         if (orderInfo.orderTakerAssetFilledAmount == 0) {
             require(
@@ -317,15 +340,69 @@ contract MixinExchangeCore is
                 "INVALID_ORDER_SIGNATURE"
             );
         }
-
-        // Validate fill order rounding
+    }
+    
+    /// @dev Validates context for fillOrder. Succeeds or throws.
+    /// @param order to be filled.
+    /// @param orderInfo OrderStatus, orderHash, and amount already filled of order.
+    /// @param takerAssetFillAmount Desired amount of order to fill by taker.
+    /// @param takerAssetFilledAmount Amount of takerAsset that will be filled.
+    /// @param makerAssetFilledAmount Amount of makerAsset that will be transfered.
+    function assertValidFill(
+        Order memory order,
+        OrderInfo memory orderInfo,
+        uint256 takerAssetFillAmount,  // TODO: use FillResults
+        uint256 takerAssetFilledAmount,
+        uint256 makerAssetFilledAmount
+    )
+        internal
+        view
+    {
+        // Revert if fill amount is invalid
+        // TODO: reconsider necessity for v2.1
+        require(
+            takerAssetFillAmount != 0,
+            "INVALID_TAKER_AMOUNT"
+        );
+        
+        // Make sure taker does not pay more than desired amount
+        // NOTE: This assertion should never fail, it is here
+        //       as an extra defence against potential bugs.
+        require(
+            takerAssetFilledAmount <= takerAssetFillAmount,
+            "TAKER_OVERPAY"
+        );
+        
+        // Make sure order is not overfilled
+        // NOTE: This assertion should never fail, it is here
+        //       as an extra defence against potential bugs.
+        require(
+            safeAdd(orderInfo.orderTakerAssetFilledAmount, takerAssetFilledAmount) <= order.takerAssetAmount,
+            "ORDER_OVERFILL"
+        );
+        
+        // Make sure order is filled at acceptable price.
+        // The order has an implied price from the makers perspective:
+        //    order price = order.makerAssetAmount / order.takerAssetAmount
+        // i.e. the number of makerAsset maker is paying per takerAsset. The
+        // maker is guaranteed to get this price or a better (lower) one. The
+        // actual price maker is getting in this fill is:
+        //    fill price = makerAssetFilledAmount / takerAssetFilledAmount
+        // We need `fill price <= order price` for the fill to be fair to maker.
+        // This amounts to:
+        //     makerAssetFilledAmount        order.makerAssetAmount
+        //    ------------------------  <=  -----------------------
+        //     takerAssetFilledAmount        order.takerAssetAmount
+        // or, equivalently:
+        //     makerAssetFilledAmount * order.takerAssetAmount <=
+        //     order.makerAssetAmount * takerAssetFilledAmount
+        // NOTE: This assertion should never fail, it is here
+        //       as an extra defence against potential bugs.
         require(
-            !isRoundingError(
-                takerAssetFilledAmount,
-                order.takerAssetAmount,
-                order.makerAssetAmount
-            ),
-            "ROUNDING_ERROR"
+            safeMul(makerAssetFilledAmount, order.takerAssetAmount)
+            <= 
+            safeMul(order.makerAssetAmount, takerAssetFilledAmount),
+            "INVALID_FILL_PRICE"
         );
     }
 
@@ -376,17 +453,17 @@ contract MixinExchangeCore is
     {
         // Compute proportional transfer amounts
         fillResults.takerAssetFilledAmount = takerAssetFilledAmount;
-        fillResults.makerAssetFilledAmount = getPartialAmount(
+        fillResults.makerAssetFilledAmount = safeGetPartialAmountFloor(
             takerAssetFilledAmount,
             order.takerAssetAmount,
             order.makerAssetAmount
         );
-        fillResults.makerFeePaid = getPartialAmount(
-            takerAssetFilledAmount,
-            order.takerAssetAmount,
+        fillResults.makerFeePaid = safeGetPartialAmountFloor(
+            fillResults.makerAssetFilledAmount,
+            order.makerAssetAmount,
             order.makerFee
         );
-        fillResults.takerFeePaid = getPartialAmount(
+        fillResults.takerFeePaid = safeGetPartialAmountFloor(
             takerAssetFilledAmount,
             order.takerAssetAmount,
             order.takerFee
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/MixinMatchOrders.sol b/packages/contracts/src/2.0.0/protocol/Exchange/MixinMatchOrders.sol
index 56b309a1b..b4f6bdb26 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/MixinMatchOrders.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/MixinMatchOrders.sol
@@ -14,6 +14,7 @@
 pragma solidity 0.4.24;
 pragma experimental ABIEncoderV2;
 
+import "../../utils/ReentrancyGuard/ReentrancyGuard.sol";
 import "./libs/LibConstants.sol";
 import "./libs/LibMath.sol";
 import "./libs/LibOrder.sol";
@@ -25,6 +26,7 @@ import "./mixins/MAssetProxyDispatcher.sol";
 
 
 contract MixinMatchOrders is
+    ReentrancyGuard,
     LibConstants,
     LibMath,
     MAssetProxyDispatcher,
@@ -48,6 +50,7 @@ contract MixinMatchOrders is
         bytes memory rightSignature
     )
         public
+        nonReentrant
         returns (LibFillResults.MatchedFillResults memory matchedFillResults)
     {
         // We assume that rightOrder.takerAssetData == leftOrder.makerAssetData and rightOrder.makerAssetData == leftOrder.takerAssetData.
@@ -61,8 +64,20 @@ contract MixinMatchOrders is
 
         // Fetch taker address
         address takerAddress = getCurrentContextAddress();
-
+        
         // Either our context is valid or we revert
+        assertFillableOrder(
+            leftOrder,
+            leftOrderInfo,
+            takerAddress,
+            leftSignature
+        );
+        assertFillableOrder(
+            rightOrder,
+            rightOrderInfo,
+            takerAddress,
+            rightSignature
+        );
         assertValidMatch(leftOrder, rightOrder);
 
         // Compute proportional fill amounts
@@ -77,20 +92,18 @@ contract MixinMatchOrders is
         assertValidFill(
             leftOrder,
             leftOrderInfo,
-            takerAddress,
             matchedFillResults.left.takerAssetFilledAmount,
             matchedFillResults.left.takerAssetFilledAmount,
-            leftSignature
+            matchedFillResults.left.makerAssetFilledAmount
         );
         assertValidFill(
             rightOrder,
             rightOrderInfo,
-            takerAddress,
             matchedFillResults.right.takerAssetFilledAmount,
             matchedFillResults.right.takerAssetFilledAmount,
-            rightSignature
+            matchedFillResults.right.makerAssetFilledAmount
         );
-
+        
         // Update exchange state
         updateFilledState(
             leftOrder,
@@ -106,7 +119,7 @@ contract MixinMatchOrders is
             rightOrderInfo.orderTakerAssetFilledAmount,
             matchedFillResults.right
         );
-    
+
         // Settle matched orders. Succeeds or throws.
         settleMatchedOrders(
             leftOrder,
@@ -162,62 +175,85 @@ contract MixinMatchOrders is
         pure
         returns (LibFillResults.MatchedFillResults memory matchedFillResults)
     {
-        // We settle orders at the exchange rate of the right order.
-        // The amount saved by the left maker goes to the taker.
-        // Either the left or right order will be fully filled; possibly both.
-        // The left order is fully filled iff the right order can sell more than left can buy.
-        // That is: the amount required to fill the left order is less than or equal to
-        //          the amount we can spend from the right order:
-        //          <leftTakerAssetAmountRemaining> <= <rightTakerAssetAmountRemaining> * <rightMakerToTakerRatio>
-        //          <leftTakerAssetAmountRemaining> <= <rightTakerAssetAmountRemaining> * <rightOrder.makerAssetAmount> / <rightOrder.takerAssetAmount>
-        //          <leftTakerAssetAmountRemaining> * <rightOrder.takerAssetAmount> <= <rightTakerAssetAmountRemaining> * <rightOrder.makerAssetAmount>
+        // Derive maker asset amounts for left & right orders, given store taker assert amounts
         uint256 leftTakerAssetAmountRemaining = safeSub(leftOrder.takerAssetAmount, leftOrderTakerAssetFilledAmount);
+        uint256 leftMakerAssetAmountRemaining = safeGetPartialAmountFloor(
+            leftOrder.makerAssetAmount,
+            leftOrder.takerAssetAmount,
+            leftTakerAssetAmountRemaining
+        );
         uint256 rightTakerAssetAmountRemaining = safeSub(rightOrder.takerAssetAmount, rightOrderTakerAssetFilledAmount);
-        uint256 leftTakerAssetFilledAmount;
-        uint256 rightTakerAssetFilledAmount;
-        if (
-            safeMul(leftTakerAssetAmountRemaining, rightOrder.takerAssetAmount) <=
-            safeMul(rightTakerAssetAmountRemaining, rightOrder.makerAssetAmount)
-        ) {
-            // Left order will be fully filled: maximally fill left
-            leftTakerAssetFilledAmount = leftTakerAssetAmountRemaining;
+        uint256 rightMakerAssetAmountRemaining = safeGetPartialAmountFloor(
+            rightOrder.makerAssetAmount,
+            rightOrder.takerAssetAmount,
+            rightTakerAssetAmountRemaining
+        );
 
-            // The right order receives an amount proportional to how much was spent.
-            rightTakerAssetFilledAmount = getPartialAmount(
-                rightOrder.takerAssetAmount,
-                rightOrder.makerAssetAmount,
-                leftTakerAssetFilledAmount
+        // Calculate fill results for maker and taker assets: at least one order will be fully filled.
+        // The maximum amount the left maker can buy is `leftTakerAssetAmountRemaining`
+        // The maximum amount the right maker can sell is `rightMakerAssetAmountRemaining`
+        // We have two distinct cases for calculating the fill results:
+        // Case 1.
+        //   If the left maker can buy more than the right maker can sell, then only the right order is fully filled.
+        //   If the left maker can buy exactly what the right maker can sell, then both orders are fully filled.
+        // Case 2.
+        //   If the left maker cannot buy more than the right maker can sell, then only the left order is fully filled.
+        if (leftTakerAssetAmountRemaining >= rightMakerAssetAmountRemaining) {
+            // Case 1: Right order is fully filled
+            matchedFillResults.right.makerAssetFilledAmount = rightMakerAssetAmountRemaining;
+            matchedFillResults.right.takerAssetFilledAmount = rightTakerAssetAmountRemaining;
+            matchedFillResults.left.takerAssetFilledAmount = matchedFillResults.right.makerAssetFilledAmount;
+            // Round down to ensure the maker's exchange rate does not exceed the price specified by the order. 
+            // We favor the maker when the exchange rate must be rounded.
+            matchedFillResults.left.makerAssetFilledAmount = safeGetPartialAmountFloor(
+                leftOrder.makerAssetAmount,
+                leftOrder.takerAssetAmount,
+                matchedFillResults.left.takerAssetFilledAmount
             );
         } else {
-            // Right order will be fully filled: maximally fill right
-            rightTakerAssetFilledAmount = rightTakerAssetAmountRemaining;
-
-            // The left order receives an amount proportional to how much was spent.
-            leftTakerAssetFilledAmount = getPartialAmount(
-                rightOrder.makerAssetAmount,
+            // Case 2: Left order is fully filled
+            matchedFillResults.left.makerAssetFilledAmount = leftMakerAssetAmountRemaining;
+            matchedFillResults.left.takerAssetFilledAmount = leftTakerAssetAmountRemaining;
+            matchedFillResults.right.makerAssetFilledAmount = matchedFillResults.left.takerAssetFilledAmount;
+            // Round up to ensure the maker's exchange rate does not exceed the price specified by the order.
+            // We favor the maker when the exchange rate must be rounded.
+            matchedFillResults.right.takerAssetFilledAmount = safeGetPartialAmountCeil(
                 rightOrder.takerAssetAmount,
-                rightTakerAssetFilledAmount
+                rightOrder.makerAssetAmount,
+                matchedFillResults.right.makerAssetFilledAmount
             );
         }
 
-        // Calculate fill results for left order
-        matchedFillResults.left = calculateFillResults(
-            leftOrder,
-            leftTakerAssetFilledAmount
-        );
-
-        // Calculate fill results for right order
-        matchedFillResults.right = calculateFillResults(
-            rightOrder,
-            rightTakerAssetFilledAmount
-        );
-
         // Calculate amount given to taker
         matchedFillResults.leftMakerAssetSpreadAmount = safeSub(
             matchedFillResults.left.makerAssetFilledAmount,
             matchedFillResults.right.takerAssetFilledAmount
         );
 
+        // Compute fees for left order
+        matchedFillResults.left.makerFeePaid = safeGetPartialAmountFloor(
+            matchedFillResults.left.makerAssetFilledAmount,
+            leftOrder.makerAssetAmount,
+            leftOrder.makerFee
+        );
+        matchedFillResults.left.takerFeePaid = safeGetPartialAmountFloor(
+            matchedFillResults.left.takerAssetFilledAmount,
+            leftOrder.takerAssetAmount,
+            leftOrder.takerFee
+        );
+
+        // Compute fees for right order
+        matchedFillResults.right.makerFeePaid = safeGetPartialAmountFloor(
+            matchedFillResults.right.makerAssetFilledAmount,
+            rightOrder.makerAssetAmount,
+            rightOrder.makerFee
+        );
+        matchedFillResults.right.takerFeePaid = safeGetPartialAmountFloor(
+            matchedFillResults.right.takerAssetFilledAmount,
+            rightOrder.takerAssetAmount,
+            rightOrder.takerFee
+        );
+
         // Return fill results
         return matchedFillResults;
     }
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/MixinSignatureValidator.sol b/packages/contracts/src/2.0.0/protocol/Exchange/MixinSignatureValidator.sol
index 44de54817..4eb6a2fa6 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/MixinSignatureValidator.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/MixinSignatureValidator.sol
@@ -19,6 +19,7 @@
 pragma solidity 0.4.24;
 
 import "../../utils/LibBytes/LibBytes.sol";
+import "../../utils/ReentrancyGuard/ReentrancyGuard.sol";
 import "./mixins/MSignatureValidator.sol";
 import "./mixins/MTransactions.sol";
 import "./interfaces/IWallet.sol";
@@ -26,6 +27,7 @@ import "./interfaces/IValidator.sol";
 
 
 contract MixinSignatureValidator is
+    ReentrancyGuard,
     MSignatureValidator,
     MTransactions
 {
@@ -48,14 +50,16 @@ contract MixinSignatureValidator is
     )
         external
     {
-        require(
-            isValidSignature(
-                hash,
-                signerAddress,
-                signature
-            ),
-            "INVALID_SIGNATURE"
-        );
+        if (signerAddress != msg.sender) {
+            require(
+                isValidSignature(
+                    hash,
+                    signerAddress,
+                    signature
+                ),
+                "INVALID_SIGNATURE"
+            );
+        }
         preSigned[hash][signerAddress] = true;
     }
 
@@ -67,6 +71,7 @@ contract MixinSignatureValidator is
         bool approval
     )
         external
+        nonReentrant
     {
         address signerAddress = getCurrentContextAddress();
         allowedValidators[signerAddress][validatorAddress] = approval;
@@ -172,26 +177,14 @@ contract MixinSignatureValidator is
             isValid = signerAddress == recovered;
             return isValid;
 
-        // Implicitly signed by caller.
-        // The signer has initiated the call. In the case of non-contract
-        // accounts it means the transaction itself was signed.
-        // Example: let's say for a particular operation three signatures
-        // A, B and C are required. To submit the transaction, A and B can
-        // give a signature to C, who can then submit the transaction using
-        // `Caller` for his own signature. Or A and C can sign and B can
-        // submit using `Caller`. Having `Caller` allows this flexibility.
-        } else if (signatureType == SignatureType.Caller) {
-            require(
-                signature.length == 0,
-                "LENGTH_0_REQUIRED"
-            );
-            isValid = signerAddress == msg.sender;
-            return isValid;
-
         // Signature verified by wallet contract.
         // If used with an order, the maker of the order is the wallet contract.
         } else if (signatureType == SignatureType.Wallet) {
-            isValid = IWallet(signerAddress).isValidSignature(hash, signature);
+            isValid = isValidWalletSignature(
+                hash,
+                signerAddress,
+                signature
+            );
             return isValid;
 
         // Signature verified by validator contract.
@@ -209,7 +202,8 @@ contract MixinSignatureValidator is
             if (!allowedValidators[signerAddress][validatorAddress]) {
                 return false;
             }
-            isValid = IValidator(validatorAddress).isValidSignature(
+            isValid = isValidValidatorSignature(
+                validatorAddress,
                 hash,
                 signerAddress,
                 signature
@@ -220,34 +214,6 @@ contract MixinSignatureValidator is
         } else if (signatureType == SignatureType.PreSigned) {
             isValid = preSigned[hash][signerAddress];
             return isValid;
-
-        // Signature from Trezor hardware wallet.
-        // It differs from web3.eth_sign in the encoding of message length
-        // (Bitcoin varint encoding vs ascii-decimal, the latter is not
-        // self-terminating which leads to ambiguities).
-        // See also:
-        // https://en.bitcoin.it/wiki/Protocol_documentation#Variable_length_integer
-        // https://github.com/trezor/trezor-mcu/blob/master/firmware/ethereum.c#L602
-        // https://github.com/trezor/trezor-mcu/blob/master/firmware/crypto.c#L36
-        } else if (signatureType == SignatureType.Trezor) {
-            require(
-                signature.length == 65,
-                "LENGTH_65_REQUIRED"
-            );
-            v = uint8(signature[0]);
-            r = signature.readBytes32(1);
-            s = signature.readBytes32(33);
-            recovered = ecrecover(
-                keccak256(abi.encodePacked(
-                    "\x19Ethereum Signed Message:\n\x20",
-                    hash
-                )),
-                v,
-                r,
-                s
-            );
-            isValid = signerAddress == recovered;
-            return isValid;
         }
 
         // Anything else is illegal (We do not return false because
@@ -257,4 +223,102 @@ contract MixinSignatureValidator is
         // signature was invalid.)
         revert("SIGNATURE_UNSUPPORTED");
     }
+
+    /// @dev Verifies signature using logic defined by Wallet contract.
+    /// @param hash Any 32 byte hash.
+    /// @param walletAddress Address that should have signed the given hash
+    ///                      and defines its own signature verification method.
+    /// @param signature Proof that the hash has been signed by signer.
+    /// @return True if signature is valid for given wallet..
+    function isValidWalletSignature(
+        bytes32 hash,
+        address walletAddress,
+        bytes signature
+    )
+        internal
+        view
+        returns (bool isValid)
+    {
+        bytes memory calldata = abi.encodeWithSelector(
+            IWallet(walletAddress).isValidSignature.selector,
+            hash,
+            signature
+        );
+        assembly {
+            let cdStart := add(calldata, 32)
+            let success := staticcall(
+                gas,              // forward all gas
+                walletAddress,    // address of Wallet contract
+                cdStart,          // pointer to start of input
+                mload(calldata),  // length of input
+                cdStart,          // write input over output
+                32                // output size is 32 bytes
+            )
+
+            switch success
+            case 0 {
+                // Revert with `Error("WALLET_ERROR")`
+                mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000)
+                mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000)
+                mstore(64, 0x0000000c57414c4c45545f4552524f5200000000000000000000000000000000)
+                mstore(96, 0)
+                revert(0, 100)
+            }
+            case 1 {
+                // Signature is valid if call did not revert and returned true
+                isValid := mload(cdStart)
+            }
+        }
+        return isValid;
+    }
+
+    /// @dev Verifies signature using logic defined by Validator contract.
+    /// @param validatorAddress Address of validator contract.
+    /// @param hash Any 32 byte hash.
+    /// @param signerAddress Address that should have signed the given hash.
+    /// @param signature Proof that the hash has been signed by signer.
+    /// @return True if the address recovered from the provided signature matches the input signer address.
+    function isValidValidatorSignature(
+        address validatorAddress,
+        bytes32 hash,
+        address signerAddress,
+        bytes signature
+    )
+        internal
+        view
+        returns (bool isValid)
+    {
+        bytes memory calldata = abi.encodeWithSelector(
+            IValidator(signerAddress).isValidSignature.selector,
+            hash,
+            signerAddress,
+            signature
+        );
+        assembly {
+            let cdStart := add(calldata, 32)
+            let success := staticcall(
+                gas,               // forward all gas
+                validatorAddress,  // address of Validator contract
+                cdStart,           // pointer to start of input
+                mload(calldata),   // length of input
+                cdStart,           // write input over output
+                32                 // output size is 32 bytes
+            )
+
+            switch success
+            case 0 {
+                // Revert with `Error("VALIDATOR_ERROR")`
+                mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000)
+                mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000)
+                mstore(64, 0x0000000f56414c494441544f525f4552524f5200000000000000000000000000)
+                mstore(96, 0)
+                revert(0, 100)
+            }
+            case 1 {
+                // Signature is valid if call did not revert and returned true
+                isValid := mload(cdStart)
+            }
+        }
+        return isValid;
+    }
 }
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/MixinTransactions.sol b/packages/contracts/src/2.0.0/protocol/Exchange/MixinTransactions.sol
index 821d30279..4a59b6c0f 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/MixinTransactions.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/MixinTransactions.sol
@@ -155,7 +155,8 @@ contract MixinTransactions is
         view
         returns (address)
     {
-        address contextAddress = currentContextAddress == address(0) ? msg.sender : currentContextAddress;
+        address currentContextAddress_ = currentContextAddress;
+        address contextAddress = currentContextAddress_ == address(0) ? msg.sender : currentContextAddress_;
         return contextAddress;
     }
 }
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol b/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol
index 86194f461..a5459a21e 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol
@@ -19,18 +19,22 @@
 pragma solidity 0.4.24;
 pragma experimental ABIEncoderV2;
 
+import "../../utils/ReentrancyGuard/ReentrancyGuard.sol";
 import "./libs/LibMath.sol";
 import "./libs/LibOrder.sol";
 import "./libs/LibFillResults.sol";
 import "./libs/LibAbiEncoder.sol";
 import "./mixins/MExchangeCore.sol";
+import "./mixins/MWrapperFunctions.sol";
 
 
 contract MixinWrapperFunctions is
+    ReentrancyGuard,
     LibMath,
     LibFillResults,
     LibAbiEncoder,
-    MExchangeCore
+    MExchangeCore,
+    MWrapperFunctions
 {
 
     /// @dev Fills the input order. Reverts if exact takerAssetFillAmount not filled.
@@ -43,17 +47,14 @@ contract MixinWrapperFunctions is
         bytes memory signature
     )
         public
+        nonReentrant
         returns (FillResults memory fillResults)
     {
-        fillResults = fillOrder(
+        fillResults = fillOrKillOrderInternal(
             order,
             takerAssetFillAmount,
             signature
         );
-        require(
-            fillResults.takerAssetFilledAmount == takerAssetFillAmount,
-            "COMPLETE_FILL_FAILED"
-        );
         return fillResults;
     }
 
@@ -88,20 +89,14 @@ contract MixinWrapperFunctions is
                 fillOrderCalldata,                  // write output over input
                 128                                 // output size is 128 bytes
             )
-            switch success
-            case 0 {
-                mstore(fillResults, 0)
-                mstore(add(fillResults, 32), 0)
-                mstore(add(fillResults, 64), 0)
-                mstore(add(fillResults, 96), 0)
-            }
-            case 1 {
+            if success {
                 mstore(fillResults, mload(fillOrderCalldata))
                 mstore(add(fillResults, 32), mload(add(fillOrderCalldata, 32)))
                 mstore(add(fillResults, 64), mload(add(fillOrderCalldata, 64)))
                 mstore(add(fillResults, 96), mload(add(fillOrderCalldata, 96)))
             }
         }
+        // fillResults values will be 0 by default if call was unsuccessful
         return fillResults;
     }
 
@@ -117,11 +112,12 @@ contract MixinWrapperFunctions is
         bytes[] memory signatures
     )
         public
+        nonReentrant
         returns (FillResults memory totalFillResults)
     {
         uint256 ordersLength = orders.length;
         for (uint256 i = 0; i != ordersLength; i++) {
-            FillResults memory singleFillResults = fillOrder(
+            FillResults memory singleFillResults = fillOrderInternal(
                 orders[i],
                 takerAssetFillAmounts[i],
                 signatures[i]
@@ -143,11 +139,12 @@ contract MixinWrapperFunctions is
         bytes[] memory signatures
     )
         public
+        nonReentrant
         returns (FillResults memory totalFillResults)
     {
         uint256 ordersLength = orders.length;
         for (uint256 i = 0; i != ordersLength; i++) {
-            FillResults memory singleFillResults = fillOrKillOrder(
+            FillResults memory singleFillResults = fillOrKillOrderInternal(
                 orders[i],
                 takerAssetFillAmounts[i],
                 signatures[i]
@@ -195,6 +192,7 @@ contract MixinWrapperFunctions is
         bytes[] memory signatures
     )
         public
+        nonReentrant
         returns (FillResults memory totalFillResults)
     {
         bytes memory takerAssetData = orders[0].takerAssetData;
@@ -210,7 +208,7 @@ contract MixinWrapperFunctions is
             uint256 remainingTakerAssetFillAmount = safeSub(takerAssetFillAmount, totalFillResults.takerAssetFilledAmount);
 
             // Attempt to sell the remaining amount of takerAsset
-            FillResults memory singleFillResults = fillOrder(
+            FillResults memory singleFillResults = fillOrderInternal(
                 orders[i],
                 remainingTakerAssetFillAmount,
                 signatures[i]
@@ -282,6 +280,7 @@ contract MixinWrapperFunctions is
         bytes[] memory signatures
     )
         public
+        nonReentrant
         returns (FillResults memory totalFillResults)
     {
         bytes memory makerAssetData = orders[0].makerAssetData;
@@ -298,14 +297,14 @@ contract MixinWrapperFunctions is
 
             // Convert the remaining amount of makerAsset to buy into remaining amount
             // of takerAsset to sell, assuming entire amount can be sold in the current order
-            uint256 remainingTakerAssetFillAmount = getPartialAmount(
+            uint256 remainingTakerAssetFillAmount = getPartialAmountFloor(
                 orders[i].takerAssetAmount,
                 orders[i].makerAssetAmount,
                 remainingMakerAssetFillAmount
             );
 
             // Attempt to sell the remaining amount of takerAsset
-            FillResults memory singleFillResults = fillOrder(
+            FillResults memory singleFillResults = fillOrderInternal(
                 orders[i],
                 remainingTakerAssetFillAmount,
                 signatures[i]
@@ -350,7 +349,7 @@ contract MixinWrapperFunctions is
 
             // Convert the remaining amount of makerAsset to buy into remaining amount
             // of takerAsset to sell, assuming entire amount can be sold in the current order
-            uint256 remainingTakerAssetFillAmount = getPartialAmount(
+            uint256 remainingTakerAssetFillAmount = getPartialAmountFloor(
                 orders[i].takerAssetAmount,
                 orders[i].makerAssetAmount,
                 remainingMakerAssetFillAmount
@@ -400,4 +399,28 @@ contract MixinWrapperFunctions is
         }
         return ordersInfo;
     }
+
+    /// @dev Fills the input order. Reverts if exact takerAssetFillAmount not filled.
+    /// @param order Order struct containing order specifications.
+    /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
+    /// @param signature Proof that order has been created by maker.
+    function fillOrKillOrderInternal(
+        LibOrder.Order memory order,
+        uint256 takerAssetFillAmount,
+        bytes memory signature
+    )
+        internal
+        returns (FillResults memory fillResults)
+    {
+        fillResults = fillOrderInternal(
+            order,
+            takerAssetFillAmount,
+            signature
+        );
+        require(
+            fillResults.takerAssetFilledAmount == takerAssetFillAmount,
+            "COMPLETE_FILL_FAILED"
+        );
+        return fillResults;
+    }
 }
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibMath.sol b/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibMath.sol
index fa09da6ac..57fd53f29 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibMath.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibMath.sol
@@ -25,12 +25,13 @@ contract LibMath is
     SafeMath
 {
 
-    /// @dev Calculates partial value given a numerator and denominator.
+    /// @dev Calculates partial value given a numerator and denominator rounded down.
+    ///      Reverts if rounding error is >= 0.1%
     /// @param numerator Numerator.
     /// @param denominator Denominator.
     /// @param target Value to calculate partial of.
-    /// @return Partial value of target.
-    function getPartialAmount(
+    /// @return Partial value of target rounded down.
+    function safeGetPartialAmountFloor(
         uint256 numerator,
         uint256 denominator,
         uint256 target
@@ -39,19 +40,133 @@ contract LibMath is
         pure
         returns (uint256 partialAmount)
     {
+        require(
+            denominator > 0,
+            "DIVISION_BY_ZERO"
+        );
+
+        require(
+            !isRoundingErrorFloor(
+                numerator,
+                denominator,
+                target
+            ),
+            "ROUNDING_ERROR"
+        );
+        
+        partialAmount = safeDiv(
+            safeMul(numerator, target),
+            denominator
+        );
+        return partialAmount;
+    }
+
+    /// @dev Calculates partial value given a numerator and denominator rounded down.
+    ///      Reverts if rounding error is >= 0.1%
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to calculate partial of.
+    /// @return Partial value of target rounded up.
+    function safeGetPartialAmountCeil(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        internal
+        pure
+        returns (uint256 partialAmount)
+    {
+        require(
+            denominator > 0,
+            "DIVISION_BY_ZERO"
+        );
+
+        require(
+            !isRoundingErrorCeil(
+                numerator,
+                denominator,
+                target
+            ),
+            "ROUNDING_ERROR"
+        );
+        
+        // safeDiv computes `floor(a / b)`. We use the identity (a, b integer):
+        //       ceil(a / b) = floor((a + b - 1) / b)
+        // To implement `ceil(a / b)` using safeDiv.
+        partialAmount = safeDiv(
+            safeAdd(
+                safeMul(numerator, target),
+                safeSub(denominator, 1)
+            ),
+            denominator
+        );
+        return partialAmount;
+    }
+
+    /// @dev Calculates partial value given a numerator and denominator rounded down.
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to calculate partial of.
+    /// @return Partial value of target rounded down.
+    function getPartialAmountFloor(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        internal
+        pure
+        returns (uint256 partialAmount)
+    {
+        require(
+            denominator > 0,
+            "DIVISION_BY_ZERO"
+        );
+
         partialAmount = safeDiv(
             safeMul(numerator, target),
             denominator
         );
         return partialAmount;
     }
+    
+    /// @dev Calculates partial value given a numerator and denominator rounded down.
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to calculate partial of.
+    /// @return Partial value of target rounded up.
+    function getPartialAmountCeil(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        internal
+        pure
+        returns (uint256 partialAmount)
+    {
+        require(
+            denominator > 0,
+            "DIVISION_BY_ZERO"
+        );
 
-    /// @dev Checks if rounding error > 0.1%.
+        // safeDiv computes `floor(a / b)`. We use the identity (a, b integer):
+        //       ceil(a / b) = floor((a + b - 1) / b)
+        // To implement `ceil(a / b)` using safeDiv.
+        partialAmount = safeDiv(
+            safeAdd(
+                safeMul(numerator, target),
+                safeSub(denominator, 1)
+            ),
+            denominator
+        );
+        return partialAmount;
+    }
+    
+    /// @dev Checks if rounding error >= 0.1% when rounding down.
     /// @param numerator Numerator.
     /// @param denominator Denominator.
     /// @param target Value to multiply with numerator/denominator.
     /// @return Rounding error is present.
-    function isRoundingError(
+    function isRoundingErrorFloor(
         uint256 numerator,
         uint256 denominator,
         uint256 target
@@ -60,16 +175,73 @@ contract LibMath is
         pure
         returns (bool isError)
     {
-        uint256 remainder = mulmod(target, numerator, denominator);
-        if (remainder == 0) {
-            return false; // No rounding error.
+        require(
+            denominator > 0,
+            "DIVISION_BY_ZERO"
+        );
+        
+        // The absolute rounding error is the difference between the rounded
+        // value and the ideal value. The relative rounding error is the
+        // absolute rounding error divided by the absolute value of the
+        // ideal value. This is undefined when the ideal value is zero.
+        //
+        // The ideal value is `numerator * target / denominator`.
+        // Let's call `numerator * target % denominator` the remainder.
+        // The absolute error is `remainder / denominator`.
+        //
+        // When the ideal value is zero, we require the absolute error to
+        // be zero. Fortunately, this is always the case. The ideal value is
+        // zero iff `numerator == 0` and/or `target == 0`. In this case the
+        // remainder and absolute error are also zero. 
+        if (target == 0 || numerator == 0) {
+            return false;
         }
-
-        uint256 errPercentageTimes1000000 = safeDiv(
-            safeMul(remainder, 1000000),
-            safeMul(numerator, target)
+        
+        // Otherwise, we want the relative rounding error to be strictly
+        // less than 0.1%.
+        // The relative error is `remainder / (numerator * target)`.
+        // We want the relative error less than 1 / 1000:
+        //        remainder / (numerator * denominator)  <  1 / 1000
+        // or equivalently:
+        //        1000 * remainder  <  numerator * target
+        // so we have a rounding error iff:
+        //        1000 * remainder  >=  numerator * target
+        uint256 remainder = mulmod(target, numerator, denominator);
+        isError = safeMul(1000, remainder) >= safeMul(numerator, target);
+        return isError;
+    }
+    
+    /// @dev Checks if rounding error >= 0.1% when rounding up.
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to multiply with numerator/denominator.
+    /// @return Rounding error is present.
+    function isRoundingErrorCeil(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        internal
+        pure
+        returns (bool isError)
+    {
+        require(
+            denominator > 0,
+            "DIVISION_BY_ZERO"
         );
-        isError = errPercentageTimes1000000 > 1000;
+        
+        // See the comments in `isRoundingError`.
+        if (target == 0 || numerator == 0) {
+            // When either is zero, the ideal value and rounded value are zero
+            // and there is no rounding error. (Although the relative error
+            // is undefined.)
+            return false;
+        }
+        // Compute remainder as before
+        uint256 remainder = mulmod(target, numerator, denominator);
+        // TODO: safeMod
+        remainder = safeSub(denominator, remainder) % denominator;
+        isError = safeMul(1000, remainder) >= safeMul(numerator, target);
         return isError;
     }
 }
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MExchangeCore.sol b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MExchangeCore.sol
index c165b647c..d85913e0f 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MExchangeCore.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MExchangeCore.sol
@@ -59,6 +59,19 @@ contract MExchangeCore is
         uint256 orderEpoch                    // Orders with specified makerAddress and senderAddress with a salt less than this value are considered cancelled.
     );
 
+    /// @dev Fills the input order.
+    /// @param order Order struct containing order specifications.
+    /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
+    /// @param signature Proof that order has been created by maker.
+    /// @return Amounts filled and fees paid by maker and taker.
+    function fillOrderInternal(
+        LibOrder.Order memory order,
+        uint256 takerAssetFillAmount,
+        bytes memory signature
+    )
+        internal
+        returns (LibFillResults.FillResults memory fillResults);
+
     /// @dev Updates state with results of a fill order.
     /// @param order that was filled.
     /// @param takerAddress Address of taker who filled the order.
@@ -83,21 +96,33 @@ contract MExchangeCore is
         bytes32 orderHash
     )
         internal;
-
+    
     /// @dev Validates context for fillOrder. Succeeds or throws.
     /// @param order to be filled.
-    /// @param orderInfo Status, orderHash, and amount already filled of order.
+    /// @param orderInfo OrderStatus, orderHash, and amount already filled of order.
     /// @param takerAddress Address of order taker.
+    /// @param signature Proof that the orders was created by its maker.
+    function assertFillableOrder(
+        LibOrder.Order memory order,
+        LibOrder.OrderInfo memory orderInfo,
+        address takerAddress,
+        bytes memory signature
+    )
+        internal
+        view;
+    
+    /// @dev Validates context for fillOrder. Succeeds or throws.
+    /// @param order to be filled.
+    /// @param orderInfo Status, orderHash, and amount already filled of order.
     /// @param takerAssetFillAmount Desired amount of order to fill by taker.
     /// @param takerAssetFilledAmount Amount of takerAsset that will be filled.
-    /// @param signature Proof that the orders was created by its maker.
+    /// @param makerAssetFilledAmount Amount of makerAsset that will be transfered.
     function assertValidFill(
         LibOrder.Order memory order,
         LibOrder.OrderInfo memory orderInfo,
-        address takerAddress,
         uint256 takerAssetFillAmount,
         uint256 takerAssetFilledAmount,
-        bytes memory signature
+        uint256 makerAssetFilledAmount
     )
         internal
         view;
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MSignatureValidator.sol b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MSignatureValidator.sol
index f14f2ba00..1fe88b908 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MSignatureValidator.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MSignatureValidator.sol
@@ -36,11 +36,40 @@ contract MSignatureValidator is
         Invalid,         // 0x01
         EIP712,          // 0x02
         EthSign,         // 0x03
-        Caller,          // 0x04
-        Wallet,          // 0x05
-        Validator,       // 0x06
-        PreSigned,       // 0x07
-        Trezor,          // 0x08
-        NSignatureTypes  // 0x09, number of signature types. Always leave at end.
+        Wallet,          // 0x04
+        Validator,       // 0x05
+        PreSigned,       // 0x06
+        NSignatureTypes  // 0x07, number of signature types. Always leave at end.
     }
+
+    /// @dev Verifies signature using logic defined by Wallet contract.
+    /// @param hash Any 32 byte hash.
+    /// @param walletAddress Address that should have signed the given hash
+    ///                      and defines its own signature verification method.
+    /// @param signature Proof that the hash has been signed by signer.
+    /// @return True if the address recovered from the provided signature matches the input signer address.
+    function isValidWalletSignature(
+        bytes32 hash,
+        address walletAddress,
+        bytes signature
+    )
+        internal
+        view
+        returns (bool isValid);
+
+    /// @dev Verifies signature using logic defined by Validator contract.
+    /// @param validatorAddress Address of validator contract.
+    /// @param hash Any 32 byte hash.
+    /// @param signerAddress Address that should have signed the given hash.
+    /// @param signature Proof that the hash has been signed by signer.
+    /// @return True if the address recovered from the provided signature matches the input signer address.
+    function isValidValidatorSignature(
+        address validatorAddress,
+        bytes32 hash,
+        address signerAddress,
+        bytes signature
+    )
+        internal
+        view
+        returns (bool isValid);
 }
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MWrapperFunctions.sol b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MWrapperFunctions.sol
new file mode 100644
index 000000000..e04d4a429
--- /dev/null
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/mixins/MWrapperFunctions.sol
@@ -0,0 +1,40 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+pragma experimental ABIEncoderV2;
+
+import "../libs/LibOrder.sol";
+import "../libs/LibFillResults.sol";
+import "../interfaces/IWrapperFunctions.sol";
+
+
+contract MWrapperFunctions {
+
+    /// @dev Fills the input order. Reverts if exact takerAssetFillAmount not filled.
+    /// @param order LibOrder.Order struct containing order specifications.
+    /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
+    /// @param signature Proof that order has been created by maker.
+    function fillOrKillOrderInternal(
+        LibOrder.Order memory order,
+        uint256 takerAssetFillAmount,
+        bytes memory signature
+    )
+        internal
+        returns (LibFillResults.FillResults memory fillResults);
+}
diff --git a/packages/contracts/src/2.0.0/test/ReentrantERC20Token/ReentrantERC20Token.sol b/packages/contracts/src/2.0.0/test/ReentrantERC20Token/ReentrantERC20Token.sol
new file mode 100644
index 000000000..4f4e28302
--- /dev/null
+++ b/packages/contracts/src/2.0.0/test/ReentrantERC20Token/ReentrantERC20Token.sol
@@ -0,0 +1,183 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+pragma experimental ABIEncoderV2;
+
+import "../../utils/LibBytes/LibBytes.sol";
+import "../../tokens/ERC20Token/ERC20Token.sol";
+import "../../protocol/Exchange/interfaces/IExchange.sol";
+import "../../protocol/Exchange/libs/LibOrder.sol";
+
+
+// solhint-disable no-unused-vars
+contract ReentrantERC20Token is
+    ERC20Token
+{
+
+    using LibBytes for bytes;
+
+    // solhint-disable-next-line var-name-mixedcase
+    IExchange internal EXCHANGE;
+
+    bytes internal constant REENTRANCY_ILLEGAL_REVERT_REASON = abi.encodeWithSelector(
+        bytes4(keccak256("Error(string)")),
+        "REENTRANCY_ILLEGAL"
+    );
+
+    // All of these functions are potentially vulnerable to reentrancy
+    // We do not test any "noThrow" functions because `fillOrderNoThrow` makes a delegatecall to `fillOrder`
+    enum ExchangeFunction {
+        FILL_ORDER,
+        FILL_OR_KILL_ORDER,
+        BATCH_FILL_ORDERS,
+        BATCH_FILL_OR_KILL_ORDERS,
+        MARKET_BUY_ORDERS,
+        MARKET_SELL_ORDERS,
+        MATCH_ORDERS,
+        CANCEL_ORDER,
+        CANCEL_ORDERS_UP_TO,
+        SET_SIGNATURE_VALIDATOR_APPROVAL
+    }
+
+    uint8 internal currentFunctionId = 0;
+
+    constructor (address _exchange)
+        public
+    {
+        EXCHANGE = IExchange(_exchange);
+    }
+
+    /// @dev Set the current function that will be called when `transferFrom` is called.
+    /// @param _currentFunctionId Id that corresponds to function name.
+    function setCurrentFunction(uint8 _currentFunctionId)
+        external
+    {
+        currentFunctionId = _currentFunctionId;
+    }
+
+    /// @dev A version of `transferFrom` that attempts to reenter the Exchange contract.
+    /// @param _from The address of the sender
+    /// @param _to The address of the recipient
+    /// @param _value The amount of token to be transferred
+    function transferFrom(
+        address _from,
+        address _to,
+        uint256 _value
+    )
+        external
+        returns (bool)
+    {
+        // This order would normally be invalid, but it will be used strictly for testing reentrnacy.
+        // Any reentrancy checks will happen before any other checks that invalidate the order.
+        LibOrder.Order memory order;
+
+        // Initialize remaining null parameters
+        bytes memory signature;
+        LibOrder.Order[] memory orders;
+        uint256[] memory takerAssetFillAmounts;
+        bytes[] memory signatures;
+        bytes memory calldata;
+
+        // Create calldata for function that corresponds to currentFunctionId
+        if (currentFunctionId == uint8(ExchangeFunction.FILL_ORDER)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.fillOrder.selector,
+                order,
+                0,
+                signature
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.FILL_OR_KILL_ORDER)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.fillOrKillOrder.selector,
+                order,
+                0,
+                signature
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.BATCH_FILL_ORDERS)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.batchFillOrders.selector,
+                orders,
+                takerAssetFillAmounts,
+                signatures
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.BATCH_FILL_OR_KILL_ORDERS)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.batchFillOrKillOrders.selector,
+                orders,
+                takerAssetFillAmounts,
+                signatures
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.MARKET_BUY_ORDERS)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.marketBuyOrders.selector,
+                orders,
+                0,
+                signatures
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.MARKET_SELL_ORDERS)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.marketSellOrders.selector,
+                orders,
+                0,
+                signatures
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.MATCH_ORDERS)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.matchOrders.selector,
+                order,
+                order,
+                signature,
+                signature
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.CANCEL_ORDER)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.cancelOrder.selector,
+                order
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.CANCEL_ORDERS_UP_TO)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.cancelOrdersUpTo.selector,
+                0
+            );
+        } else if (currentFunctionId == uint8(ExchangeFunction.SET_SIGNATURE_VALIDATOR_APPROVAL)) {
+            calldata = abi.encodeWithSelector(
+                EXCHANGE.setSignatureValidatorApproval.selector,
+                address(0),
+                false
+            );
+        }
+
+        // Call Exchange function, swallow error
+        address(EXCHANGE).call(calldata);
+
+        // Revert reason is 100 bytes
+        bytes memory returnData = new bytes(100);
+
+        // Copy return data
+        assembly {
+            returndatacopy(add(returnData, 32), 0, 100)
+        }
+
+        // Revert if function reverted with REENTRANCY_ILLEGAL error
+        require(!REENTRANCY_ILLEGAL_REVERT_REASON.equals(returnData));
+
+        // Transfer will return true if function failed for any other reason
+        return true;
+    }
+}
\ No newline at end of file
diff --git a/packages/contracts/src/2.0.0/test/TestExchangeInternals/TestExchangeInternals.sol b/packages/contracts/src/2.0.0/test/TestExchangeInternals/TestExchangeInternals.sol
index d9cec9edc..27187f8f8 100644
--- a/packages/contracts/src/2.0.0/test/TestExchangeInternals/TestExchangeInternals.sol
+++ b/packages/contracts/src/2.0.0/test/TestExchangeInternals/TestExchangeInternals.sol
@@ -63,11 +63,12 @@ contract TestExchangeInternals is
     }
 
     /// @dev Calculates partial value given a numerator and denominator.
+    ///      Reverts if rounding error is >= 0.1%
     /// @param numerator Numerator.
     /// @param denominator Denominator.
     /// @param target Value to calculate partial of.
     /// @return Partial value of target.
-    function publicGetPartialAmount(
+    function publicSafeGetPartialAmountFloor(
         uint256 numerator,
         uint256 denominator,
         uint256 target
@@ -76,15 +77,84 @@ contract TestExchangeInternals is
         pure
         returns (uint256 partialAmount)
     {
-        return getPartialAmount(numerator, denominator, target);
+        return safeGetPartialAmountFloor(numerator, denominator, target);
     }
 
-    /// @dev Checks if rounding error > 0.1%.
+    /// @dev Calculates partial value given a numerator and denominator.
+    ///      Reverts if rounding error is >= 0.1%
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to calculate partial of.
+    /// @return Partial value of target.
+    function publicSafeGetPartialAmountCeil(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        public
+        pure
+        returns (uint256 partialAmount)
+    {
+        return safeGetPartialAmountCeil(numerator, denominator, target);
+    }
+
+    /// @dev Calculates partial value given a numerator and denominator.
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to calculate partial of.
+    /// @return Partial value of target.
+    function publicGetPartialAmountFloor(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        public
+        pure
+        returns (uint256 partialAmount)
+    {
+        return getPartialAmountFloor(numerator, denominator, target);
+    }
+
+    /// @dev Calculates partial value given a numerator and denominator.
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to calculate partial of.
+    /// @return Partial value of target.
+    function publicGetPartialAmountCeil(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        public
+        pure
+        returns (uint256 partialAmount)
+    {
+        return getPartialAmountCeil(numerator, denominator, target);
+    }
+
+    /// @dev Checks if rounding error >= 0.1%.
+    /// @param numerator Numerator.
+    /// @param denominator Denominator.
+    /// @param target Value to multiply with numerator/denominator.
+    /// @return Rounding error is present.
+    function publicIsRoundingErrorFloor(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        public
+        pure
+        returns (bool isError)
+    {
+        return isRoundingErrorFloor(numerator, denominator, target);
+    }
+
+    /// @dev Checks if rounding error >= 0.1%.
     /// @param numerator Numerator.
     /// @param denominator Denominator.
     /// @param target Value to multiply with numerator/denominator.
     /// @return Rounding error is present.
-    function publicIsRoundingError(
+    function publicIsRoundingErrorCeil(
         uint256 numerator,
         uint256 denominator,
         uint256 target
@@ -93,7 +163,7 @@ contract TestExchangeInternals is
         pure
         returns (bool isError)
     {
-        return isRoundingError(numerator, denominator, target);
+        return isRoundingErrorCeil(numerator, denominator, target);
     }
  
     /// @dev Updates state with results of a fill order.
diff --git a/packages/contracts/src/2.0.0/test/TestLibs/TestLibs.sol b/packages/contracts/src/2.0.0/test/TestLibs/TestLibs.sol
index 4a99dd9c1..c8c58545f 100644
--- a/packages/contracts/src/2.0.0/test/TestLibs/TestLibs.sol
+++ b/packages/contracts/src/2.0.0/test/TestLibs/TestLibs.sol
@@ -49,7 +49,7 @@ contract TestLibs is
         return fillOrderCalldata;
     }
 
-    function publicGetPartialAmount(
+    function publicGetPartialAmountFloor(
         uint256 numerator,
         uint256 denominator,
         uint256 target
@@ -58,7 +58,7 @@ contract TestLibs is
         pure
         returns (uint256 partialAmount)
     {
-        partialAmount = getPartialAmount(
+        partialAmount = getPartialAmountFloor(
             numerator,
             denominator,
             target
@@ -66,7 +66,41 @@ contract TestLibs is
         return partialAmount;
     }
 
-    function publicIsRoundingError(
+    function publicGetPartialAmountCeil(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        public
+        pure
+        returns (uint256 partialAmount)
+    {
+        partialAmount = getPartialAmountCeil(
+            numerator,
+            denominator,
+            target
+        );
+        return partialAmount;
+    }
+
+    function publicIsRoundingErrorFloor(
+        uint256 numerator,
+        uint256 denominator,
+        uint256 target
+    )
+        public
+        pure
+        returns (bool isError)
+    {
+        isError = isRoundingErrorFloor(
+            numerator,
+            denominator,
+            target
+        );
+        return isError;
+    }
+
+    function publicIsRoundingErrorCeil(
         uint256 numerator,
         uint256 denominator,
         uint256 target
@@ -75,7 +109,7 @@ contract TestLibs is
         pure
         returns (bool isError)
     {
-        isError = isRoundingError(
+        isError = isRoundingErrorCeil(
             numerator,
             denominator,
             target
diff --git a/packages/contracts/src/2.0.0/test/TestStaticCallReceiver/TestStaticCallReceiver.sol b/packages/contracts/src/2.0.0/test/TestStaticCallReceiver/TestStaticCallReceiver.sol
new file mode 100644
index 000000000..41aab01c8
--- /dev/null
+++ b/packages/contracts/src/2.0.0/test/TestStaticCallReceiver/TestStaticCallReceiver.sol
@@ -0,0 +1,81 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+
+import "../../tokens/ERC20Token/IERC20Token.sol";
+
+
+// solhint-disable no-unused-vars
+contract TestStaticCallReceiver {
+
+    uint256 internal state = 1;
+
+    /// @dev Updates state and returns true. Intended to be used with `Validator` signature type.
+    /// @param hash Message hash that is signed.
+    /// @param signerAddress Address that should have signed the given hash.
+    /// @param signature Proof of signing.
+    /// @return Validity of order signature.
+    function isValidSignature(
+        bytes32 hash,
+        address signerAddress,
+        bytes signature
+    )
+        external
+        returns (bool isValid)
+    {
+        updateState();
+        return true;
+    }
+
+    /// @dev Updates state and returns true. Intended to be used with `Wallet` signature type.
+    /// @param hash Message hash that is signed.
+    /// @param signature Proof of signing.
+    /// @return Validity of order signature.
+    function isValidSignature(
+        bytes32 hash,
+        bytes signature
+    )
+        external
+        returns (bool isValid)
+    {
+        updateState();
+        return true;
+    }
+
+    /// @dev Approves an ERC20 token to spend tokens from this address.
+    /// @param token Address of ERC20 token.
+    /// @param spender Address that will spend tokens.
+    /// @param value Amount of tokens spender is approved to spend.
+    function approveERC20(
+        address token,
+        address spender,
+        uint256 value
+    )
+        external
+    {
+        IERC20Token(token).approve(spender, value);
+    }
+
+    /// @dev Increments state variable.
+    function updateState()
+        internal
+    {
+        state++;
+    }
+}
diff --git a/packages/contracts/src/2.0.0/utils/ReentrancyGuard/ReentrancyGuard.sol b/packages/contracts/src/2.0.0/utils/ReentrancyGuard/ReentrancyGuard.sol
new file mode 100644
index 000000000..1dee512d4
--- /dev/null
+++ b/packages/contracts/src/2.0.0/utils/ReentrancyGuard/ReentrancyGuard.sol
@@ -0,0 +1,44 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+pragma solidity 0.4.24;
+
+
+contract ReentrancyGuard {
+
+    // Locked state of mutex
+    bool private locked = false;
+
+    /// @dev Functions with this modifer cannot be reentered. The mutex will be locked
+    ///      before function execution and unlocked after.
+    modifier nonReentrant() {
+        // Ensure mutex is unlocked
+        require(
+            !locked,
+            "REENTRANCY_ILLEGAL"
+        );
+
+        // Lock mutex before function call
+        locked = true;
+
+        // Perform function call
+        _;
+
+        // Unlock mutex after function call
+        locked = false;
+    }
+}
diff --git a/packages/contracts/test/asset_proxy/proxies.ts b/packages/contracts/test/asset_proxy/proxies.ts
index 76a020222..6031e554d 100644
--- a/packages/contracts/test/asset_proxy/proxies.ts
+++ b/packages/contracts/test/asset_proxy/proxies.ts
@@ -12,7 +12,7 @@ import { ERC20ProxyContract } from '../../generated_contract_wrappers/erc20_prox
 import { ERC721ProxyContract } from '../../generated_contract_wrappers/erc721_proxy';
 import { IAssetProxyContract } from '../../generated_contract_wrappers/i_asset_proxy';
 import { artifacts } from '../utils/artifacts';
-import { expectTransactionFailedAsync } from '../utils/assertions';
+import { expectTransactionFailedAsync, expectTransactionFailedWithoutReasonAsync } from '../utils/assertions';
 import { chaiSetup } from '../utils/chai_setup';
 import { constants } from '../utils/constants';
 import { ERC20Wrapper } from '../utils/erc20_wrapper';
@@ -99,6 +99,17 @@ describe('Asset Transfer Proxies', () => {
         await blockchainLifecycle.revertAsync();
     });
     describe('Transfer Proxy - ERC20', () => {
+        it('should revert if undefined function is called', async () => {
+            const undefinedSelector = '0x01020304';
+            await expectTransactionFailedWithoutReasonAsync(
+                web3Wrapper.sendTransactionAsync({
+                    from: owner,
+                    to: erc20Proxy.address,
+                    value: constants.ZERO_AMOUNT,
+                    data: undefinedSelector,
+                }),
+            );
+        });
         describe('transferFrom', () => {
             it('should successfully transfer tokens', async () => {
                 // Construct ERC20 asset data
@@ -219,6 +230,17 @@ describe('Asset Transfer Proxies', () => {
     });
 
     describe('Transfer Proxy - ERC721', () => {
+        it('should revert if undefined function is called', async () => {
+            const undefinedSelector = '0x01020304';
+            await expectTransactionFailedWithoutReasonAsync(
+                web3Wrapper.sendTransactionAsync({
+                    from: owner,
+                    to: erc721Proxy.address,
+                    value: constants.ZERO_AMOUNT,
+                    data: undefinedSelector,
+                }),
+            );
+        });
         describe('transferFrom', () => {
             it('should successfully transfer tokens', async () => {
                 // Construct ERC721 asset data
diff --git a/packages/contracts/test/exchange/core.ts b/packages/contracts/test/exchange/core.ts
index bc2bad749..3bb71b58f 100644
--- a/packages/contracts/test/exchange/core.ts
+++ b/packages/contracts/test/exchange/core.ts
@@ -1,6 +1,6 @@
 import { BlockchainLifecycle } from '@0xproject/dev-utils';
 import { assetDataUtils, orderHashUtils } from '@0xproject/order-utils';
-import { RevertReason, SignedOrder } from '@0xproject/types';
+import { RevertReason, SignatureType, SignedOrder } from '@0xproject/types';
 import { BigNumber } from '@0xproject/utils';
 import { Web3Wrapper } from '@0xproject/web3-wrapper';
 import * as chai from 'chai';
@@ -14,6 +14,8 @@ import { DummyNoReturnERC20TokenContract } from '../../generated_contract_wrappe
 import { ERC20ProxyContract } from '../../generated_contract_wrappers/erc20_proxy';
 import { ERC721ProxyContract } from '../../generated_contract_wrappers/erc721_proxy';
 import { ExchangeCancelEventArgs, ExchangeContract } from '../../generated_contract_wrappers/exchange';
+import { ReentrantERC20TokenContract } from '../../generated_contract_wrappers/reentrant_erc20_token';
+import { TestStaticCallReceiverContract } from '../../generated_contract_wrappers/test_static_call_receiver';
 import { artifacts } from '../utils/artifacts';
 import { expectTransactionFailedAsync } from '../utils/assertions';
 import { getLatestBlockTimestampAsync, increaseTimeAndMineBlockAsync } from '../utils/block_timestamp';
@@ -41,9 +43,12 @@ describe('Exchange core', () => {
     let zrxToken: DummyERC20TokenContract;
     let erc721Token: DummyERC721TokenContract;
     let noReturnErc20Token: DummyNoReturnERC20TokenContract;
+    let reentrantErc20Token: ReentrantERC20TokenContract;
     let exchange: ExchangeContract;
     let erc20Proxy: ERC20ProxyContract;
     let erc721Proxy: ERC721ProxyContract;
+    let maliciousWallet: TestStaticCallReceiverContract;
+    let maliciousValidator: TestStaticCallReceiverContract;
 
     let signedOrder: SignedOrder;
     let erc20Balances: ERC20BalancesByOwner;
@@ -109,6 +114,18 @@ describe('Exchange core', () => {
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
 
+        maliciousWallet = maliciousValidator = await TestStaticCallReceiverContract.deployFrom0xArtifactAsync(
+            artifacts.TestStaticCallReceiver,
+            provider,
+            txDefaults,
+        );
+        reentrantErc20Token = await ReentrantERC20TokenContract.deployFrom0xArtifactAsync(
+            artifacts.ReentrantERC20Token,
+            provider,
+            txDefaults,
+            exchange.address,
+        );
+
         defaultMakerAssetAddress = erc20TokenA.address;
         defaultTakerAssetAddress = erc20TokenB.address;
 
@@ -135,6 +152,26 @@ describe('Exchange core', () => {
             signedOrder = await orderFactory.newSignedOrderAsync();
         });
 
+        const reentrancyTest = (functionNames: string[]) => {
+            _.forEach(functionNames, async (functionName: string, functionId: number) => {
+                const description = `should not allow fillOrder to reenter the Exchange contract via ${functionName}`;
+                it(description, async () => {
+                    signedOrder = await orderFactory.newSignedOrderAsync({
+                        makerAssetData: assetDataUtils.encodeERC20AssetData(reentrantErc20Token.address),
+                    });
+                    await web3Wrapper.awaitTransactionSuccessAsync(
+                        await reentrantErc20Token.setCurrentFunction.sendTransactionAsync(functionId),
+                        constants.AWAIT_TRANSACTION_MINED_MS,
+                    );
+                    await expectTransactionFailedAsync(
+                        exchangeWrapper.fillOrderAsync(signedOrder, takerAddress),
+                        RevertReason.TransferFailed,
+                    );
+                });
+            });
+        };
+        describe('fillOrder reentrancy tests', () => reentrancyTest(constants.FUNCTIONS_WITH_MUTEX));
+
         it('should throw if signature is invalid', async () => {
             signedOrder = await orderFactory.newSignedOrderAsync({
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
@@ -161,6 +198,51 @@ describe('Exchange core', () => {
                 RevertReason.OrderUnfillable,
             );
         });
+
+        it('should revert if `isValidSignature` tries to update state when SignatureType=Wallet', async () => {
+            const maliciousMakerAddress = maliciousWallet.address;
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await erc20TokenA.setBalance.sendTransactionAsync(
+                    maliciousMakerAddress,
+                    constants.INITIAL_ERC20_BALANCE,
+                ),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await maliciousWallet.approveERC20.sendTransactionAsync(
+                    erc20TokenA.address,
+                    erc20Proxy.address,
+                    constants.INITIAL_ERC20_ALLOWANCE,
+                ),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            signedOrder = await orderFactory.newSignedOrderAsync({
+                makerAddress: maliciousMakerAddress,
+                makerFee: constants.ZERO_AMOUNT,
+            });
+            signedOrder.signature = `0x0${SignatureType.Wallet}`;
+            await expectTransactionFailedAsync(
+                exchangeWrapper.fillOrderAsync(signedOrder, takerAddress),
+                RevertReason.WalletError,
+            );
+        });
+
+        it('should revert if `isValidSignature` tries to update state when SignatureType=Validator', async () => {
+            const isApproved = true;
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await exchange.setSignatureValidatorApproval.sendTransactionAsync(
+                    maliciousValidator.address,
+                    isApproved,
+                    { from: makerAddress },
+                ),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            signedOrder.signature = `${maliciousValidator.address}0${SignatureType.Validator}`;
+            await expectTransactionFailedAsync(
+                exchangeWrapper.fillOrderAsync(signedOrder, takerAddress),
+                RevertReason.ValidatorError,
+            );
+        });
     });
 
     describe('Testing exchange of ERC20 tokens with no return values', () => {
@@ -448,7 +530,7 @@ describe('Exchange core', () => {
                 // HACK(albrow): We need to hardcode the gas estimate here because
                 // the Geth gas estimator doesn't work with the way we use
                 // delegatecall and swallow errors.
-                gas: 490000,
+                gas: 600000,
             });
 
             const newBalances = await erc20Wrapper.getBalancesAsync();
diff --git a/packages/contracts/test/exchange/internal.ts b/packages/contracts/test/exchange/internal.ts
index 67d1d2d2c..dc2c5fbe0 100644
--- a/packages/contracts/test/exchange/internal.ts
+++ b/packages/contracts/test/exchange/internal.ts
@@ -1,6 +1,7 @@
 import { BlockchainLifecycle } from '@0xproject/dev-utils';
 import { Order, RevertReason, SignedOrder } from '@0xproject/types';
 import { BigNumber } from '@0xproject/utils';
+import * as chai from 'chai';
 import * as _ from 'lodash';
 
 import { TestExchangeInternalsContract } from '../../generated_contract_wrappers/test_exchange_internals';
@@ -16,6 +17,8 @@ import { FillResults } from '../utils/types';
 import { provider, txDefaults, web3Wrapper } from '../utils/web3_wrapper';
 
 chaiSetup.configure();
+const expect = chai.expect;
+
 const blockchainLifecycle = new BlockchainLifecycle(web3Wrapper);
 
 const MAX_UINT256 = new BigNumber(2).pow(256).minus(1);
@@ -43,26 +46,11 @@ const emptySignedOrder: SignedOrder = {
 
 const overflowErrorForCall = new Error(RevertReason.Uint256Overflow);
 
-async function referenceGetPartialAmountAsync(
-    numerator: BigNumber,
-    denominator: BigNumber,
-    target: BigNumber,
-): Promise<BigNumber> {
-    const invalidOpcodeErrorForCall = new Error(await getInvalidOpcodeErrorMessageForCallAsync());
-    const product = numerator.mul(target);
-    if (product.greaterThan(MAX_UINT256)) {
-        throw overflowErrorForCall;
-    }
-    if (denominator.eq(0)) {
-        throw invalidOpcodeErrorForCall;
-    }
-    return product.dividedToIntegerBy(denominator);
-}
-
 describe('Exchange core internal functions', () => {
     let testExchange: TestExchangeInternalsContract;
-    let invalidOpcodeErrorForCall: Error | undefined;
     let overflowErrorForSendTransaction: Error | undefined;
+    let divisionByZeroErrorForCall: Error | undefined;
+    let roundingErrorForCall: Error | undefined;
 
     before(async () => {
         await blockchainLifecycle.startAsync();
@@ -79,11 +67,86 @@ describe('Exchange core internal functions', () => {
         overflowErrorForSendTransaction = new Error(
             await getRevertReasonOrErrorMessageForSendTransactionAsync(RevertReason.Uint256Overflow),
         );
-        invalidOpcodeErrorForCall = new Error(await getInvalidOpcodeErrorMessageForCallAsync());
+        divisionByZeroErrorForCall = new Error(RevertReason.DivisionByZero);
+        roundingErrorForCall = new Error(RevertReason.RoundingError);
     });
     // Note(albrow): Don't forget to add beforeEach and afterEach calls to reset
     // the blockchain state for any tests which modify it!
 
+    async function referenceIsRoundingErrorFloorAsync(
+        numerator: BigNumber,
+        denominator: BigNumber,
+        target: BigNumber,
+    ): Promise<boolean> {
+        if (denominator.eq(0)) {
+            throw divisionByZeroErrorForCall;
+        }
+        if (numerator.eq(0)) {
+            return false;
+        }
+        if (target.eq(0)) {
+            return false;
+        }
+        const product = numerator.mul(target);
+        const remainder = product.mod(denominator);
+        const remainderTimes1000 = remainder.mul('1000');
+        const isError = remainderTimes1000.gte(product);
+        if (product.greaterThan(MAX_UINT256)) {
+            throw overflowErrorForCall;
+        }
+        if (remainderTimes1000.greaterThan(MAX_UINT256)) {
+            throw overflowErrorForCall;
+        }
+        return isError;
+    }
+
+    async function referenceIsRoundingErrorCeilAsync(
+        numerator: BigNumber,
+        denominator: BigNumber,
+        target: BigNumber,
+    ): Promise<boolean> {
+        if (denominator.eq(0)) {
+            throw divisionByZeroErrorForCall;
+        }
+        if (numerator.eq(0)) {
+            return false;
+        }
+        if (target.eq(0)) {
+            return false;
+        }
+        const product = numerator.mul(target);
+        const remainder = product.mod(denominator);
+        const error = denominator.sub(remainder).mod(denominator);
+        const errorTimes1000 = error.mul('1000');
+        const isError = errorTimes1000.gte(product);
+        if (product.greaterThan(MAX_UINT256)) {
+            throw overflowErrorForCall;
+        }
+        if (errorTimes1000.greaterThan(MAX_UINT256)) {
+            throw overflowErrorForCall;
+        }
+        return isError;
+    }
+
+    async function referenceSafeGetPartialAmountFloorAsync(
+        numerator: BigNumber,
+        denominator: BigNumber,
+        target: BigNumber,
+    ): Promise<BigNumber> {
+        if (denominator.eq(0)) {
+            throw divisionByZeroErrorForCall;
+        }
+        const isRoundingError = await referenceIsRoundingErrorFloorAsync(numerator, denominator, target);
+        if (isRoundingError) {
+            throw roundingErrorForCall;
+        }
+        const product = numerator.mul(target);
+        if (product.greaterThan(MAX_UINT256)) {
+            throw overflowErrorForCall;
+        }
+        return product.dividedToIntegerBy(denominator);
+    }
+
     describe('addFillResults', async () => {
         function makeFillResults(value: BigNumber): FillResults {
             return {
@@ -158,19 +221,22 @@ describe('Exchange core internal functions', () => {
             // in any mathematical operation in either the reference TypeScript
             // implementation or the Solidity implementation of
             // calculateFillResults.
+            const makerAssetFilledAmount = await referenceSafeGetPartialAmountFloorAsync(
+                takerAssetFilledAmount,
+                orderTakerAssetAmount,
+                otherAmount,
+            );
+            const order = makeOrder(otherAmount, orderTakerAssetAmount, otherAmount, otherAmount);
+            const orderMakerAssetAmount = order.makerAssetAmount;
             return {
-                makerAssetFilledAmount: await referenceGetPartialAmountAsync(
-                    takerAssetFilledAmount,
-                    orderTakerAssetAmount,
-                    otherAmount,
-                ),
+                makerAssetFilledAmount,
                 takerAssetFilledAmount,
-                makerFeePaid: await referenceGetPartialAmountAsync(
-                    takerAssetFilledAmount,
-                    orderTakerAssetAmount,
+                makerFeePaid: await referenceSafeGetPartialAmountFloorAsync(
+                    makerAssetFilledAmount,
+                    orderMakerAssetAmount,
                     otherAmount,
                 ),
-                takerFeePaid: await referenceGetPartialAmountAsync(
+                takerFeePaid: await referenceSafeGetPartialAmountFloorAsync(
                     takerAssetFilledAmount,
                     orderTakerAssetAmount,
                     otherAmount,
@@ -193,60 +259,158 @@ describe('Exchange core internal functions', () => {
         );
     });
 
-    describe('getPartialAmount', async () => {
-        async function testGetPartialAmountAsync(
+    describe('getPartialAmountFloor', async () => {
+        async function referenceGetPartialAmountFloorAsync(
             numerator: BigNumber,
             denominator: BigNumber,
             target: BigNumber,
         ): Promise<BigNumber> {
-            return testExchange.publicGetPartialAmount.callAsync(numerator, denominator, target);
+            if (denominator.eq(0)) {
+                throw divisionByZeroErrorForCall;
+            }
+            const product = numerator.mul(target);
+            if (product.greaterThan(MAX_UINT256)) {
+                throw overflowErrorForCall;
+            }
+            return product.dividedToIntegerBy(denominator);
+        }
+        async function testGetPartialAmountFloorAsync(
+            numerator: BigNumber,
+            denominator: BigNumber,
+            target: BigNumber,
+        ): Promise<BigNumber> {
+            return testExchange.publicGetPartialAmountFloor.callAsync(numerator, denominator, target);
         }
         await testCombinatoriallyWithReferenceFuncAsync(
-            'getPartialAmount',
-            referenceGetPartialAmountAsync,
-            testGetPartialAmountAsync,
+            'getPartialAmountFloor',
+            referenceGetPartialAmountFloorAsync,
+            testGetPartialAmountFloorAsync,
             [uint256Values, uint256Values, uint256Values],
         );
     });
 
-    describe('isRoundingError', async () => {
-        async function referenceIsRoundingErrorAsync(
+    describe('getPartialAmountCeil', async () => {
+        async function referenceGetPartialAmountCeilAsync(
             numerator: BigNumber,
             denominator: BigNumber,
             target: BigNumber,
-        ): Promise<boolean> {
-            const product = numerator.mul(target);
+        ): Promise<BigNumber> {
             if (denominator.eq(0)) {
-                throw invalidOpcodeErrorForCall;
-            }
-            const remainder = product.mod(denominator);
-            if (remainder.eq(0)) {
-                return false;
+                throw divisionByZeroErrorForCall;
             }
-            if (product.greaterThan(MAX_UINT256)) {
+            const product = numerator.mul(target);
+            const offset = product.add(denominator.sub(1));
+            if (offset.greaterThan(MAX_UINT256)) {
                 throw overflowErrorForCall;
             }
-            if (product.eq(0)) {
-                throw invalidOpcodeErrorForCall;
+            const result = offset.dividedToIntegerBy(denominator);
+            if (product.mod(denominator).eq(0)) {
+                expect(result.mul(denominator)).to.be.bignumber.eq(product);
+            } else {
+                expect(result.mul(denominator)).to.be.bignumber.gt(product);
             }
-            const remainderTimes1000000 = remainder.mul('1000000');
-            if (remainderTimes1000000.greaterThan(MAX_UINT256)) {
+            return result;
+        }
+        async function testGetPartialAmountCeilAsync(
+            numerator: BigNumber,
+            denominator: BigNumber,
+            target: BigNumber,
+        ): Promise<BigNumber> {
+            return testExchange.publicGetPartialAmountCeil.callAsync(numerator, denominator, target);
+        }
+        await testCombinatoriallyWithReferenceFuncAsync(
+            'getPartialAmountCeil',
+            referenceGetPartialAmountCeilAsync,
+            testGetPartialAmountCeilAsync,
+            [uint256Values, uint256Values, uint256Values],
+        );
+    });
+
+    describe('safeGetPartialAmountFloor', async () => {
+        async function testSafeGetPartialAmountFloorAsync(
+            numerator: BigNumber,
+            denominator: BigNumber,
+            target: BigNumber,
+        ): Promise<BigNumber> {
+            return testExchange.publicSafeGetPartialAmountFloor.callAsync(numerator, denominator, target);
+        }
+        await testCombinatoriallyWithReferenceFuncAsync(
+            'safeGetPartialAmountFloor',
+            referenceSafeGetPartialAmountFloorAsync,
+            testSafeGetPartialAmountFloorAsync,
+            [uint256Values, uint256Values, uint256Values],
+        );
+    });
+
+    describe('safeGetPartialAmountCeil', async () => {
+        async function referenceSafeGetPartialAmountCeilAsync(
+            numerator: BigNumber,
+            denominator: BigNumber,
+            target: BigNumber,
+        ): Promise<BigNumber> {
+            if (denominator.eq(0)) {
+                throw divisionByZeroErrorForCall;
+            }
+            const isRoundingError = await referenceIsRoundingErrorCeilAsync(numerator, denominator, target);
+            if (isRoundingError) {
+                throw roundingErrorForCall;
+            }
+            const product = numerator.mul(target);
+            const offset = product.add(denominator.sub(1));
+            if (offset.greaterThan(MAX_UINT256)) {
                 throw overflowErrorForCall;
             }
-            const errPercentageTimes1000000 = remainderTimes1000000.dividedToIntegerBy(product);
-            return errPercentageTimes1000000.greaterThan('1000');
+            const result = offset.dividedToIntegerBy(denominator);
+            if (product.mod(denominator).eq(0)) {
+                expect(result.mul(denominator)).to.be.bignumber.eq(product);
+            } else {
+                expect(result.mul(denominator)).to.be.bignumber.gt(product);
+            }
+            return result;
+        }
+        async function testSafeGetPartialAmountCeilAsync(
+            numerator: BigNumber,
+            denominator: BigNumber,
+            target: BigNumber,
+        ): Promise<BigNumber> {
+            return testExchange.publicSafeGetPartialAmountCeil.callAsync(numerator, denominator, target);
+        }
+        await testCombinatoriallyWithReferenceFuncAsync(
+            'safeGetPartialAmountCeil',
+            referenceSafeGetPartialAmountCeilAsync,
+            testSafeGetPartialAmountCeilAsync,
+            [uint256Values, uint256Values, uint256Values],
+        );
+    });
+
+    describe('isRoundingErrorFloor', async () => {
+        async function testIsRoundingErrorFloorAsync(
+            numerator: BigNumber,
+            denominator: BigNumber,
+            target: BigNumber,
+        ): Promise<boolean> {
+            return testExchange.publicIsRoundingErrorFloor.callAsync(numerator, denominator, target);
         }
-        async function testIsRoundingErrorAsync(
+        await testCombinatoriallyWithReferenceFuncAsync(
+            'isRoundingErrorFloor',
+            referenceIsRoundingErrorFloorAsync,
+            testIsRoundingErrorFloorAsync,
+            [uint256Values, uint256Values, uint256Values],
+        );
+    });
+
+    describe('isRoundingErrorCeil', async () => {
+        async function testIsRoundingErrorCeilAsync(
             numerator: BigNumber,
             denominator: BigNumber,
             target: BigNumber,
         ): Promise<boolean> {
-            return testExchange.publicIsRoundingError.callAsync(numerator, denominator, target);
+            return testExchange.publicIsRoundingErrorCeil.callAsync(numerator, denominator, target);
         }
         await testCombinatoriallyWithReferenceFuncAsync(
-            'isRoundingError',
-            referenceIsRoundingErrorAsync,
-            testIsRoundingErrorAsync,
+            'isRoundingErrorCeil',
+            referenceIsRoundingErrorCeilAsync,
+            testIsRoundingErrorCeilAsync,
             [uint256Values, uint256Values, uint256Values],
         );
     });
diff --git a/packages/contracts/test/exchange/libs.ts b/packages/contracts/test/exchange/libs.ts
index 6c3305d1d..37234489e 100644
--- a/packages/contracts/test/exchange/libs.ts
+++ b/packages/contracts/test/exchange/libs.ts
@@ -71,29 +71,57 @@ describe('Exchange libs', () => {
     // combinatorial tests in test/exchange/internal. They test specific edge
     // cases that are not covered by the combinatorial tests.
     describe('LibMath', () => {
-        it('should return false if there is a rounding error of 0.1%', async () => {
-            const numerator = new BigNumber(20);
-            const denominator = new BigNumber(999);
-            const target = new BigNumber(50);
-            // rounding error = ((20*50/999) - floor(20*50/999)) / (20*50/999) = 0.1%
-            const isRoundingError = await libs.publicIsRoundingError.callAsync(numerator, denominator, target);
-            expect(isRoundingError).to.be.false();
-        });
-        it('should return false if there is a rounding of 0.09%', async () => {
-            const numerator = new BigNumber(20);
-            const denominator = new BigNumber(9991);
-            const target = new BigNumber(500);
-            // rounding error = ((20*500/9991) - floor(20*500/9991)) / (20*500/9991) = 0.09%
-            const isRoundingError = await libs.publicIsRoundingError.callAsync(numerator, denominator, target);
-            expect(isRoundingError).to.be.false();
+        describe('isRoundingError', () => {
+            it('should return true if there is a rounding error of 0.1%', async () => {
+                const numerator = new BigNumber(20);
+                const denominator = new BigNumber(999);
+                const target = new BigNumber(50);
+                // rounding error = ((20*50/999) - floor(20*50/999)) / (20*50/999) = 0.1%
+                const isRoundingError = await libs.publicIsRoundingErrorFloor.callAsync(numerator, denominator, target);
+                expect(isRoundingError).to.be.true();
+            });
+            it('should return false if there is a rounding of 0.09%', async () => {
+                const numerator = new BigNumber(20);
+                const denominator = new BigNumber(9991);
+                const target = new BigNumber(500);
+                // rounding error = ((20*500/9991) - floor(20*500/9991)) / (20*500/9991) = 0.09%
+                const isRoundingError = await libs.publicIsRoundingErrorFloor.callAsync(numerator, denominator, target);
+                expect(isRoundingError).to.be.false();
+            });
+            it('should return true if there is a rounding error of 0.11%', async () => {
+                const numerator = new BigNumber(20);
+                const denominator = new BigNumber(9989);
+                const target = new BigNumber(500);
+                // rounding error = ((20*500/9989) - floor(20*500/9989)) / (20*500/9989) = 0.011%
+                const isRoundingError = await libs.publicIsRoundingErrorFloor.callAsync(numerator, denominator, target);
+                expect(isRoundingError).to.be.true();
+            });
         });
-        it('should return true if there is a rounding error of 0.11%', async () => {
-            const numerator = new BigNumber(20);
-            const denominator = new BigNumber(9989);
-            const target = new BigNumber(500);
-            // rounding error = ((20*500/9989) - floor(20*500/9989)) / (20*500/9989) = 0.011%
-            const isRoundingError = await libs.publicIsRoundingError.callAsync(numerator, denominator, target);
-            expect(isRoundingError).to.be.true();
+        describe('isRoundingErrorCeil', () => {
+            it('should return true if there is a rounding error of 0.1%', async () => {
+                const numerator = new BigNumber(20);
+                const denominator = new BigNumber(1001);
+                const target = new BigNumber(50);
+                // rounding error = (ceil(20*50/1001) - (20*50/1001)) / (20*50/1001) = 0.1%
+                const isRoundingError = await libs.publicIsRoundingErrorCeil.callAsync(numerator, denominator, target);
+                expect(isRoundingError).to.be.true();
+            });
+            it('should return false if there is a rounding of 0.09%', async () => {
+                const numerator = new BigNumber(20);
+                const denominator = new BigNumber(10009);
+                const target = new BigNumber(500);
+                // rounding error = (ceil(20*500/10009) - (20*500/10009)) / (20*500/10009) = 0.09%
+                const isRoundingError = await libs.publicIsRoundingErrorCeil.callAsync(numerator, denominator, target);
+                expect(isRoundingError).to.be.false();
+            });
+            it('should return true if there is a rounding error of 0.11%', async () => {
+                const numerator = new BigNumber(20);
+                const denominator = new BigNumber(10011);
+                const target = new BigNumber(500);
+                // rounding error = (ceil(20*500/10011) - (20*500/10011)) / (20*500/10011) = 0.11%
+                const isRoundingError = await libs.publicIsRoundingErrorCeil.callAsync(numerator, denominator, target);
+                expect(isRoundingError).to.be.true();
+            });
         });
     });
 
diff --git a/packages/contracts/test/exchange/match_orders.ts b/packages/contracts/test/exchange/match_orders.ts
index 46b3569bd..554c456cc 100644
--- a/packages/contracts/test/exchange/match_orders.ts
+++ b/packages/contracts/test/exchange/match_orders.ts
@@ -11,6 +11,8 @@ import { DummyERC721TokenContract } from '../../generated_contract_wrappers/dumm
 import { ERC20ProxyContract } from '../../generated_contract_wrappers/erc20_proxy';
 import { ERC721ProxyContract } from '../../generated_contract_wrappers/erc721_proxy';
 import { ExchangeContract } from '../../generated_contract_wrappers/exchange';
+import { ReentrantERC20TokenContract } from '../../generated_contract_wrappers/reentrant_erc20_token';
+import { TestExchangeInternalsContract } from '../../generated_contract_wrappers/test_exchange_internals';
 import { artifacts } from '../utils/artifacts';
 import { expectTransactionFailedAsync } from '../utils/assertions';
 import { chaiSetup } from '../utils/chai_setup';
@@ -20,12 +22,12 @@ import { ERC721Wrapper } from '../utils/erc721_wrapper';
 import { ExchangeWrapper } from '../utils/exchange_wrapper';
 import { MatchOrderTester } from '../utils/match_order_tester';
 import { OrderFactory } from '../utils/order_factory';
-import { ERC20BalancesByOwner, ERC721TokenIdsByOwner, OrderInfo, OrderStatus } from '../utils/types';
+import { ERC20BalancesByOwner, ERC721TokenIdsByOwner } from '../utils/types';
 import { provider, txDefaults, web3Wrapper } from '../utils/web3_wrapper';
 
+const blockchainLifecycle = new BlockchainLifecycle(web3Wrapper);
 chaiSetup.configure();
 const expect = chai.expect;
-const blockchainLifecycle = new BlockchainLifecycle(web3Wrapper);
 
 describe('matchOrders', () => {
     let makerAddressLeft: string;
@@ -39,6 +41,7 @@ describe('matchOrders', () => {
     let erc20TokenB: DummyERC20TokenContract;
     let zrxToken: DummyERC20TokenContract;
     let erc721Token: DummyERC721TokenContract;
+    let reentrantErc20Token: ReentrantERC20TokenContract;
     let exchange: ExchangeContract;
     let erc20Proxy: ERC20ProxyContract;
     let erc721Proxy: ERC721ProxyContract;
@@ -60,6 +63,8 @@ describe('matchOrders', () => {
 
     let matchOrderTester: MatchOrderTester;
 
+    let testExchange: TestExchangeInternalsContract;
+
     before(async () => {
         await blockchainLifecycle.startAsync();
     });
@@ -127,23 +132,46 @@ describe('matchOrders', () => {
             }),
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
+
+        reentrantErc20Token = await ReentrantERC20TokenContract.deployFrom0xArtifactAsync(
+            artifacts.ReentrantERC20Token,
+            provider,
+            txDefaults,
+            exchange.address,
+        );
+
         // Set default addresses
         defaultERC20MakerAssetAddress = erc20TokenA.address;
         defaultERC20TakerAssetAddress = erc20TokenB.address;
         defaultERC721AssetAddress = erc721Token.address;
         // Create default order parameters
-        const defaultOrderParams = {
+        const defaultOrderParamsLeft = {
             ...constants.STATIC_ORDER_PARAMS,
+            makerAddress: makerAddressLeft,
             exchangeAddress: exchange.address,
             makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
             takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
+            feeRecipientAddress: feeRecipientAddressLeft,
+        };
+        const defaultOrderParamsRight = {
+            ...constants.STATIC_ORDER_PARAMS,
+            makerAddress: makerAddressRight,
+            exchangeAddress: exchange.address,
+            makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
+            takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
+            feeRecipientAddress: feeRecipientAddressRight,
         };
         const privateKeyLeft = constants.TESTRPC_PRIVATE_KEYS[accounts.indexOf(makerAddressLeft)];
-        orderFactoryLeft = new OrderFactory(privateKeyLeft, defaultOrderParams);
+        orderFactoryLeft = new OrderFactory(privateKeyLeft, defaultOrderParamsLeft);
         const privateKeyRight = constants.TESTRPC_PRIVATE_KEYS[accounts.indexOf(makerAddressRight)];
-        orderFactoryRight = new OrderFactory(privateKeyRight, defaultOrderParams);
+        orderFactoryRight = new OrderFactory(privateKeyRight, defaultOrderParamsRight);
         // Set match order tester
         matchOrderTester = new MatchOrderTester(exchangeWrapper, erc20Wrapper, erc721Wrapper, zrxToken.address);
+        testExchange = await TestExchangeInternalsContract.deployFrom0xArtifactAsync(
+            artifacts.TestExchangeInternals,
+            provider,
+            txDefaults,
+        );
     });
     beforeEach(async () => {
         await blockchainLifecycle.startAsync();
@@ -157,263 +185,580 @@ describe('matchOrders', () => {
             erc721TokenIdsByOwner = await erc721Wrapper.getBalancesAsync();
         });
 
-        it('should transfer the correct amounts when orders completely fill each other', async () => {
+        it('Should transfer correct amounts when right order is fully filled and values pass isRoundingErrorFloor but fail isRoundingErrorCeil', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
                 makerAddress: makerAddressLeft,
-                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(17), 0),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(98), 0),
                 feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
                 makerAddress: makerAddressRight,
                 makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
                 takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
-                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(75), 0),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(13), 0),
                 feeRecipientAddress: feeRecipientAddressRight,
             });
+            // Assert is rounding error ceil & not rounding error floor
+            // These assertions are taken from MixinMatchOrders::calculateMatchedFillResults
+            // The rounding error is derived computating how much the left maker will sell.
+            const numerator = signedOrderLeft.makerAssetAmount;
+            const denominator = signedOrderLeft.takerAssetAmount;
+            const target = signedOrderRight.makerAssetAmount;
+            const isRoundingErrorCeil = await testExchange.publicIsRoundingErrorCeil.callAsync(
+                numerator,
+                denominator,
+                target,
+            );
+            expect(isRoundingErrorCeil).to.be.true();
+            const isRoundingErrorFloor = await testExchange.publicIsRoundingErrorFloor.callAsync(
+                numerator,
+                denominator,
+                target,
+            );
+            expect(isRoundingErrorFloor).to.be.false();
             // Match signedOrderLeft with signedOrderRight
-            await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            // Note that the left maker received a slightly better sell price.
+            // This is intentional; see note in MixinMatchOrders.calculateMatchedFillResults.
+            // Because the left maker received a slightly more favorable sell price, the fee
+            // paid by the left taker is slightly higher than that paid by the left maker.
+            // Fees can be thought of as a tax paid by the seller, derived from the sale price.
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(13), 0),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(75), 0),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber('76.4705882352941176'), 16), // 76.47%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(75), 0),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(13), 0),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(0), 0),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber('76.5306122448979591'), 16), // 76.53%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+            };
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight,
                 takerAddress,
                 erc20BalancesByOwner,
                 erc721TokenIdsByOwner,
+                expectedTransferAmounts,
             );
-            // Verify left order was fully filled
-            const leftOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderLeft);
-            expect(leftOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FULLY_FILLED);
-            // Verify right order was fully filled
-            const rightOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderRight);
-            expect(rightOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FULLY_FILLED);
         });
 
-        it('should transfer the correct amounts when orders completely fill each other and taker doesnt take a profit', async () => {
+        it('Should transfer correct amounts when left order is fully filled and values pass isRoundingErrorCeil but fail isRoundingErrorFloor', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
                 makerAddress: makerAddressLeft,
-                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(15), 0),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(90), 0),
                 feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
                 makerAddress: makerAddressRight,
                 makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
                 takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
-                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(97), 0),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(14), 0),
                 feeRecipientAddress: feeRecipientAddressRight,
             });
-            // Store original taker balance
-            const takerInitialBalances = _.cloneDeep(erc20BalancesByOwner[takerAddress][defaultERC20MakerAssetAddress]);
+            // Assert is rounding error floor & not rounding error ceil
+            // These assertions are taken from MixinMatchOrders::calculateMatchedFillResults
+            // The rounding error is derived computating how much the right maker will buy.
+            const numerator = signedOrderRight.takerAssetAmount;
+            const denominator = signedOrderRight.makerAssetAmount;
+            const target = signedOrderLeft.takerAssetAmount;
+            const isRoundingErrorFloor = await testExchange.publicIsRoundingErrorFloor.callAsync(
+                numerator,
+                denominator,
+                target,
+            );
+            expect(isRoundingErrorFloor).to.be.true();
+            const isRoundingErrorCeil = await testExchange.publicIsRoundingErrorCeil.callAsync(
+                numerator,
+                denominator,
+                target,
+            );
+            expect(isRoundingErrorCeil).to.be.false();
             // Match signedOrderLeft with signedOrderRight
-            let newERC20BalancesByOwner: ERC20BalancesByOwner;
-            let newERC721TokenIdsByOwner: ERC721TokenIdsByOwner;
-            // prettier-ignore
-            [
-                newERC20BalancesByOwner,
-                // tslint:disable-next-line:trailing-comma
-                newERC721TokenIdsByOwner
-            ] = await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            // Note that the right maker received a slightly better purchase price.
+            // This is intentional; see note in MixinMatchOrders.calculateMatchedFillResults.
+            // Because the right maker received a slightly more favorable buy price, the fee
+            // paid by the right taker is slightly higher than that paid by the right maker.
+            // Fees can be thought of as a tax paid by the seller, derived from the sale price.
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(15), 0),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(90), 0),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(90), 0),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(13), 0),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber('92.7835051546391752'), 16), // 92.78%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 0),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber('92.8571428571428571'), 16), // 92.85%
+            };
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight,
                 takerAddress,
                 erc20BalancesByOwner,
                 erc721TokenIdsByOwner,
-            );
-            // Verify left order was fully filled
-            const leftOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderLeft);
-            expect(leftOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FULLY_FILLED);
-            // Verify right order was fully filled
-            const rightOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderRight);
-            expect(rightOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FULLY_FILLED);
-            // Verify taker did not take a profit
-            expect(takerInitialBalances).to.be.deep.equal(
-                newERC20BalancesByOwner[takerAddress][defaultERC20MakerAssetAddress],
+                expectedTransferAmounts,
             );
         });
 
-        it('should transfer the correct amounts when left order is completely filled and right order is partially filled', async () => {
+        it('Should give right maker a better buy price when rounding', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
                 makerAddress: makerAddressLeft,
-                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(16), 0),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(22), 0),
                 feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
                 makerAddress: makerAddressRight,
                 makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
                 takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
-                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(20), 18),
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(4), 18),
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(83), 0),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(49), 0),
                 feeRecipientAddress: feeRecipientAddressRight,
             });
-            // Match orders
-            await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            // Note:
+            // The correct price buy price for the right maker would yield (49/83) * 22 = 12.988 units
+            // of the left maker asset. This gets rounded up to 13, giving the right maker a better price.
+            // Note:
+            //  The maker/taker fee percentage paid on the right order differs because
+            //  they received different sale prices. The right maker pays a
+            //  fee slightly lower than the right taker.
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(16), 0),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(22), 0),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(22), 0),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(13), 0),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber('26.5060240963855421'), 16), // 26.506%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(3), 0),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber('26.5306122448979591'), 16), // 26.531%
+            };
+            // Match signedOrderLeft with signedOrderRight
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight,
                 takerAddress,
                 erc20BalancesByOwner,
                 erc721TokenIdsByOwner,
+                expectedTransferAmounts,
             );
-            // Verify left order was fully filled
-            const leftOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderLeft);
-            expect(leftOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FULLY_FILLED);
-            // Verify right order was partially filled
-            const rightOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderRight);
-            expect(rightOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FILLABLE);
         });
 
-        it('should transfer the correct amounts when right order is completely filled and left order is partially filled', async () => {
+        it('Should give left maker a better sell price when rounding', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
                 makerAddress: makerAddressLeft,
-                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(50), 18),
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 18),
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(12), 0),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(97), 0),
                 feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
                 makerAddress: makerAddressRight,
                 makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
                 takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
-                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(89), 0),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), 0),
                 feeRecipientAddress: feeRecipientAddressRight,
             });
-            // Match orders
-            await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            // Note:
+            //  The maker/taker fee percentage paid on the left order differs because
+            //  they received different sale prices. The left maker pays a fee
+            //  slightly lower than the left taker.
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(11), 0),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(89), 0),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber('91.6666666666666666'), 16), // 91.6%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(89), 0),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), 0),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 0),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber('91.7525773195876288'), 16), // 91.75%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+            };
+            // Match signedOrderLeft with signedOrderRight
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight,
                 takerAddress,
                 erc20BalancesByOwner,
                 erc721TokenIdsByOwner,
+                expectedTransferAmounts,
             );
-            // Verify left order was partially filled
-            const leftOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderLeft);
-            expect(leftOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FILLABLE);
-            // Verify right order was fully filled
-            const rightOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderRight);
-            expect(rightOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FULLY_FILLED);
         });
 
-        it('should transfer the correct amounts when consecutive calls are used to completely fill the left order', async () => {
+        it('Should transfer correct amounts when right order fill amount deviates from amount derived by `Exchange.fillOrder`', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
                 makerAddress: makerAddressLeft,
-                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(50), 18),
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 18),
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(1000), 0),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(1005), 0),
                 feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
                 makerAddress: makerAddressRight,
                 makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
                 takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2126), 0),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(1063), 0),
+                feeRecipientAddress: feeRecipientAddressRight,
+            });
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(1000), 0),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(1005), 0),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                // Notes:
+                //  i.
+                //    The left order is fully filled by the right order, so the right maker must sell 1005 units of their asset to the left maker.
+                //    By selling 1005 units, the right maker should theoretically receive 502.5 units of the left maker's asset.
+                //    Since the transfer amount must be an integer, this value must be rounded down to 502 or up to 503.
+                //  ii.
+                //    If the right order were filled via `Exchange.fillOrder` the respective fill amounts would be [1004, 502] or [1006, 503].
+                //    It follows that we cannot trigger a sale of 1005 units of the right maker's asset through `Exchange.fillOrder`.
+                //  iii.
+                //    For an optimal match, the algorithm must choose either [1005, 502] or [1005, 503] as fill amounts for the right order.
+                //    The algorithm favors the right maker when the exchange rate must be rounded, so the final fill for the right order is [1005, 503].
+                //  iv.
+                //    The right maker fee differs from the right taker fee because their exchange rate differs.
+                //    The right maker always receives the better exchange and fee price.
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(1005), 0),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(503), 0),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber('47.2718720602069614'), 16), // 47.27%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(497), 0),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber('47.3189087488240827'), 16), // 47.31%
+            };
+            // Match signedOrderLeft with signedOrderRight
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
+                signedOrderLeft,
+                signedOrderRight,
+                takerAddress,
+                erc20BalancesByOwner,
+                erc721TokenIdsByOwner,
+                expectedTransferAmounts,
+            );
+        });
+
+        const reentrancyTest = (functionNames: string[]) => {
+            _.forEach(functionNames, async (functionName: string, functionId: number) => {
+                const description = `should not allow matchOrders to reenter the Exchange contract via ${functionName}`;
+                it(description, async () => {
+                    const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                        makerAssetData: assetDataUtils.encodeERC20AssetData(reentrantErc20Token.address),
+                        makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                        takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                    });
+                    const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                        makerAddress: makerAddressRight,
+                        takerAssetData: assetDataUtils.encodeERC20AssetData(reentrantErc20Token.address),
+                        makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                        takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                        feeRecipientAddress: feeRecipientAddressRight,
+                    });
+                    await web3Wrapper.awaitTransactionSuccessAsync(
+                        await reentrantErc20Token.setCurrentFunction.sendTransactionAsync(functionId),
+                        constants.AWAIT_TRANSACTION_MINED_MS,
+                    );
+                    await expectTransactionFailedAsync(
+                        exchangeWrapper.matchOrdersAsync(signedOrderLeft, signedOrderRight, takerAddress),
+                        RevertReason.TransferFailed,
+                    );
+                });
+            });
+        };
+        describe('matchOrders reentrancy tests', () => reentrancyTest(constants.FUNCTIONS_WITH_MUTEX));
+
+        it('should transfer the correct amounts when orders completely fill each other', async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+            });
+            // Match signedOrderLeft with signedOrderRight
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(3), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+            };
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
+                signedOrderLeft,
+                signedOrderRight,
+                takerAddress,
+                erc20BalancesByOwner,
+                erc721TokenIdsByOwner,
+                expectedTransferAmounts,
+            );
+        });
+
+        it('should transfer the correct amounts when orders completely fill each other and taker doesnt take a profit', async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+            });
+            // Match signedOrderLeft with signedOrderRight
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(0), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+            };
+            // Match signedOrderLeft with signedOrderRight
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
+                signedOrderLeft,
+                signedOrderRight,
+                takerAddress,
+                erc20BalancesByOwner,
+                erc721TokenIdsByOwner,
+                expectedTransferAmounts,
+            );
+        });
+
+        it('should transfer the correct amounts when left order is completely filled and right order is partially filled', async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(20), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(4), 18),
+            });
+            // Match signedOrderLeft with signedOrderRight
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(50), 16), // 50%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(3), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(50), 16), // 50%
+            };
+            // Match signedOrderLeft with signedOrderRight
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
+                signedOrderLeft,
+                signedOrderRight,
+                takerAddress,
+                erc20BalancesByOwner,
+                erc721TokenIdsByOwner,
+                expectedTransferAmounts,
+            );
+        });
+
+        it('should transfer the correct amounts when right order is completely filled and left order is partially filled', async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(50), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+            });
+            // Match signedOrderLeft with signedOrderRight
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 16), // 10%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(3), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 16), // 10%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+            };
+            // Match signedOrderLeft with signedOrderRight
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
+                signedOrderLeft,
+                signedOrderRight,
+                takerAddress,
+                erc20BalancesByOwner,
+                erc721TokenIdsByOwner,
+                expectedTransferAmounts,
+            );
+        });
+
+        it('should transfer the correct amounts when consecutive calls are used to completely fill the left order', async () => {
+            // Create orders to match
+            const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
+                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(50), 18),
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 18),
+            });
+            const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
-                feeRecipientAddress: feeRecipientAddressRight,
             });
             // Match orders
             let newERC20BalancesByOwner: ERC20BalancesByOwner;
             let newERC721TokenIdsByOwner: ERC721TokenIdsByOwner;
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 16), // 10%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(3), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 16), // 10%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+            };
             // prettier-ignore
             [
                 newERC20BalancesByOwner,
                 // tslint:disable-next-line:trailing-comma
                 newERC721TokenIdsByOwner
-            ] = await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            ] = await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight,
                 takerAddress,
                 erc20BalancesByOwner,
                 erc721TokenIdsByOwner,
+                expectedTransferAmounts,
             );
-            // Verify left order was partially filled
-            const leftOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderLeft);
-            expect(leftOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FILLABLE);
-            // Verify right order was fully filled
-            const rightOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderRight);
-            expect(rightOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FULLY_FILLED);
             // Construct second right order
             // Note: This order needs makerAssetAmount=90/takerAssetAmount=[anything <= 45] to fully fill the right order.
             //       However, we use 100/50 to ensure a partial fill as we want to go down the "left fill"
             //       branch in the contract twice for this test.
             const signedOrderRight2 = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
-                takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(50), 18),
-                feeRecipientAddress: feeRecipientAddressRight,
             });
             // Match signedOrderLeft with signedOrderRight2
             const leftTakerAssetFilledAmount = signedOrderRight.makerAssetAmount;
             const rightTakerAssetFilledAmount = new BigNumber(0);
-            await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            const expectedTransferAmounts2 = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(45), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(90), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(90), 16), // 90% (10% paid earlier)
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(90), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(45), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(90), 16), // 90%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(0), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(90), 16), // 90% (10% paid earlier)
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(90), 16), // 90%
+            };
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight2,
                 takerAddress,
                 newERC20BalancesByOwner,
-                erc721TokenIdsByOwner,
+                newERC721TokenIdsByOwner,
+                expectedTransferAmounts2,
                 leftTakerAssetFilledAmount,
                 rightTakerAssetFilledAmount,
             );
-            // Verify left order was fully filled
-            const leftOrderInfo2: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderLeft);
-            expect(leftOrderInfo2.orderStatus as OrderStatus).to.be.equal(OrderStatus.FULLY_FILLED);
-            // Verify second right order was partially filled
-            const rightOrderInfo2: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderRight2);
-            expect(rightOrderInfo2.orderStatus as OrderStatus).to.be.equal(OrderStatus.FILLABLE);
         });
 
         it('should transfer the correct amounts when consecutive calls are used to completely fill the right order', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
-                feeRecipientAddress: feeRecipientAddressLeft,
             });
 
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
-                takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(50), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 18),
-                feeRecipientAddress: feeRecipientAddressRight,
             });
             // Match orders
             let newERC20BalancesByOwner: ERC20BalancesByOwner;
             let newERC721TokenIdsByOwner: ERC721TokenIdsByOwner;
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(4), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(4), 16), // 4%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(6), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(4), 16), // 4%
+            };
             // prettier-ignore
             [
                 newERC20BalancesByOwner,
                 // tslint:disable-next-line:trailing-comma
                 newERC721TokenIdsByOwner
-            ] = await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            ] = await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight,
                 takerAddress,
                 erc20BalancesByOwner,
                 erc721TokenIdsByOwner,
+                expectedTransferAmounts,
             );
-            // Verify left order was partially filled
-            const leftOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderLeft);
-            expect(leftOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FULLY_FILLED);
-            // Verify right order was fully filled
-            const rightOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderRight);
-            expect(rightOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FILLABLE);
+
             // Create second left order
             // Note: This order needs makerAssetAmount=96/takerAssetAmount=48 to fully fill the right order.
             //       However, we use 100/50 to ensure a partial fill as we want to go down the "right fill"
             //       branch in the contract twice for this test.
             const signedOrderLeft2 = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(50), 18),
-                feeRecipientAddress: feeRecipientAddressLeft,
             });
             // Match signedOrderLeft2 with signedOrderRight
             const leftTakerAssetFilledAmount = new BigNumber(0);
@@ -421,198 +766,257 @@ describe('matchOrders', () => {
                 erc20BalancesByOwner[takerAddress][defaultERC20MakerAssetAddress],
             );
             const rightTakerAssetFilledAmount = signedOrderLeft.makerAssetAmount.minus(takerAmountReceived);
-            await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            const expectedTransferAmounts2 = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(96), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(48), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(96), 16), // 96%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(48), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(96), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(96), 16), // 96%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(0), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(96), 16), // 96%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(96), 16), // 96%
+            };
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft2,
                 signedOrderRight,
                 takerAddress,
                 newERC20BalancesByOwner,
-                erc721TokenIdsByOwner,
+                newERC721TokenIdsByOwner,
+                expectedTransferAmounts2,
                 leftTakerAssetFilledAmount,
                 rightTakerAssetFilledAmount,
             );
-            // Verify second left order was partially filled
-            const leftOrderInfo2: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderLeft2);
-            expect(leftOrderInfo2.orderStatus as OrderStatus).to.be.equal(OrderStatus.FILLABLE);
-            // Verify right order was fully filled
-            const rightOrderInfo2: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderRight);
-            expect(rightOrderInfo2.orderStatus as OrderStatus).to.be.equal(OrderStatus.FULLY_FILLED);
         });
 
         it('should transfer the correct amounts if fee recipient is the same across both matched orders', async () => {
             const feeRecipientAddress = feeRecipientAddressLeft;
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 feeRecipientAddress,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
-                takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
                 feeRecipientAddress,
             });
             // Match orders
-            await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(3), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+            };
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight,
                 takerAddress,
                 erc20BalancesByOwner,
                 erc721TokenIdsByOwner,
+                expectedTransferAmounts,
             );
         });
 
         it('should transfer the correct amounts if taker is also the left order maker', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
-                feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
-                takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
-                feeRecipientAddress: feeRecipientAddressRight,
             });
             // Match orders
             takerAddress = signedOrderLeft.makerAddress;
-            await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(3), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+            };
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight,
                 takerAddress,
                 erc20BalancesByOwner,
                 erc721TokenIdsByOwner,
+                expectedTransferAmounts,
             );
         });
 
         it('should transfer the correct amounts if taker is also the right order maker', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
-                feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
-                takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
-                feeRecipientAddress: feeRecipientAddressRight,
             });
             // Match orders
             takerAddress = signedOrderRight.makerAddress;
-            await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(3), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+            };
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight,
                 takerAddress,
                 erc20BalancesByOwner,
                 erc721TokenIdsByOwner,
+                expectedTransferAmounts,
             );
         });
 
         it('should transfer the correct amounts if taker is also the left fee recipient', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
-                feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
-                takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
-                feeRecipientAddress: feeRecipientAddressRight,
             });
             // Match orders
             takerAddress = feeRecipientAddressLeft;
-            await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(3), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+            };
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight,
                 takerAddress,
                 erc20BalancesByOwner,
                 erc721TokenIdsByOwner,
+                expectedTransferAmounts,
             );
         });
 
         it('should transfer the correct amounts if taker is also the right fee recipient', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
-                feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
-                takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
-                feeRecipientAddress: feeRecipientAddressRight,
             });
             // Match orders
             takerAddress = feeRecipientAddressRight;
-            await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(3), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+            };
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight,
                 takerAddress,
                 erc20BalancesByOwner,
                 erc721TokenIdsByOwner,
+                expectedTransferAmounts,
             );
         });
 
         it('should transfer the correct amounts if left maker is the left fee recipient and right maker is the right fee recipient', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
-                feeRecipientAddress: makerAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
-                takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
-                feeRecipientAddress: makerAddressRight,
             });
             // Match orders
-            await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(3), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+            };
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight,
                 takerAddress,
                 erc20BalancesByOwner,
                 erc721TokenIdsByOwner,
+                expectedTransferAmounts,
             );
         });
 
         it('Should throw if left order is not fillable', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
-                feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
-                takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
-                feeRecipientAddress: feeRecipientAddressRight,
             });
             // Cancel left order
             await exchangeWrapper.cancelOrderAsync(signedOrderLeft, signedOrderLeft.makerAddress);
@@ -626,18 +1030,12 @@ describe('matchOrders', () => {
         it('Should throw if right order is not fillable', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
-                feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
-                takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
-                feeRecipientAddress: feeRecipientAddressRight,
             });
             // Cancel right order
             await exchangeWrapper.cancelOrderAsync(signedOrderRight, signedOrderRight.makerAddress);
@@ -651,18 +1049,12 @@ describe('matchOrders', () => {
         it('should throw if there is not a positive spread', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 18),
-                feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
-                takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(200), 18),
-                feeRecipientAddress: feeRecipientAddressRight,
             });
             // Match orders
             return expectTransactionFailedAsync(
@@ -674,18 +1066,13 @@ describe('matchOrders', () => {
         it('should throw if the left maker asset is not equal to the right taker asset ', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
-                feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
                 takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
-                feeRecipientAddress: feeRecipientAddressRight,
             });
             // Match orders
             return expectTransactionFailedAsync(
@@ -701,20 +1088,13 @@ describe('matchOrders', () => {
         it('should throw if the right maker asset is not equal to the left taker asset', async () => {
             // Create orders to match
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(5), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
-                feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
-                takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
-                feeRecipientAddress: feeRecipientAddressRight,
             });
             // Match orders
             return expectTransactionFailedAsync(
@@ -727,70 +1107,76 @@ describe('matchOrders', () => {
             // Create orders to match
             const erc721TokenToTransfer = erc721LeftMakerAssetIds[0];
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
                 makerAssetData: assetDataUtils.encodeERC721AssetData(defaultERC721AssetAddress, erc721TokenToTransfer),
-                takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
                 makerAssetAmount: new BigNumber(1),
                 takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
-                feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20TakerAssetAddress),
                 takerAssetData: assetDataUtils.encodeERC721AssetData(defaultERC721AssetAddress, erc721TokenToTransfer),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 takerAssetAmount: new BigNumber(1),
-                feeRecipientAddress: feeRecipientAddressRight,
             });
             // Match orders
-            await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), 0),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), 0),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(0), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 50%
+            };
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight,
                 takerAddress,
                 erc20BalancesByOwner,
                 erc721TokenIdsByOwner,
+                expectedTransferAmounts,
             );
-            // Verify left order was fully filled
-            const leftOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderLeft);
-            expect(leftOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FULLY_FILLED);
-            // Verify right order was fully filled
-            const rightOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderRight);
-            expect(rightOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FULLY_FILLED);
         });
 
         it('should transfer correct amounts when right order maker asset is an ERC721 token', async () => {
             // Create orders to match
             const erc721TokenToTransfer = erc721RightMakerAssetIds[0];
             const signedOrderLeft = await orderFactoryLeft.newSignedOrderAsync({
-                makerAddress: makerAddressLeft,
-                makerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 takerAssetData: assetDataUtils.encodeERC721AssetData(defaultERC721AssetAddress, erc721TokenToTransfer),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
                 takerAssetAmount: new BigNumber(1),
-                feeRecipientAddress: feeRecipientAddressLeft,
             });
             const signedOrderRight = await orderFactoryRight.newSignedOrderAsync({
-                makerAddress: makerAddressRight,
                 makerAssetData: assetDataUtils.encodeERC721AssetData(defaultERC721AssetAddress, erc721TokenToTransfer),
-                takerAssetData: assetDataUtils.encodeERC20AssetData(defaultERC20MakerAssetAddress),
                 makerAssetAmount: new BigNumber(1),
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
-                feeRecipientAddress: feeRecipientAddressRight,
+                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(8), 18),
             });
             // Match orders
-            await matchOrderTester.matchOrdersAndVerifyBalancesAsync(
+            const expectedTransferAmounts = {
+                // Left Maker
+                amountSoldByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), 18),
+                amountBoughtByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), 0),
+                feePaidByLeftMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Right Maker
+                amountSoldByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), 0),
+                amountBoughtByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(8), 18),
+                feePaidByRightMaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                // Taker
+                amountReceivedByTaker: Web3Wrapper.toBaseUnitAmount(new BigNumber(2), 18),
+                feePaidByTakerLeft: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+                feePaidByTakerRight: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 16), // 100%
+            };
+            await matchOrderTester.matchOrdersAndAssertEffectsAsync(
                 signedOrderLeft,
                 signedOrderRight,
                 takerAddress,
                 erc20BalancesByOwner,
                 erc721TokenIdsByOwner,
+                expectedTransferAmounts,
             );
-            // Verify left order was fully filled
-            const leftOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderLeft);
-            expect(leftOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FULLY_FILLED);
-            // Verify right order was fully filled
-            const rightOrderInfo: OrderInfo = await exchangeWrapper.getOrderInfoAsync(signedOrderRight);
-            expect(rightOrderInfo.orderStatus as OrderStatus).to.be.equal(OrderStatus.FULLY_FILLED);
         });
     });
 }); // tslint:disable-line:max-file-line-count
diff --git a/packages/contracts/test/exchange/signature_validator.ts b/packages/contracts/test/exchange/signature_validator.ts
index cd4f3d6f3..da2febfd8 100644
--- a/packages/contracts/test/exchange/signature_validator.ts
+++ b/packages/contracts/test/exchange/signature_validator.ts
@@ -9,11 +9,12 @@ import {
     TestSignatureValidatorContract,
     TestSignatureValidatorSignatureValidatorApprovalEventArgs,
 } from '../../generated_contract_wrappers/test_signature_validator';
+import { TestStaticCallReceiverContract } from '../../generated_contract_wrappers/test_static_call_receiver';
 import { ValidatorContract } from '../../generated_contract_wrappers/validator';
 import { WalletContract } from '../../generated_contract_wrappers/wallet';
 import { addressUtils } from '../utils/address_utils';
 import { artifacts } from '../utils/artifacts';
-import { expectContractCallFailed } from '../utils/assertions';
+import { expectContractCallFailed, expectContractCallFailedWithoutReasonAsync } from '../utils/assertions';
 import { chaiSetup } from '../utils/chai_setup';
 import { constants } from '../utils/constants';
 import { LogDecoder } from '../utils/log_decoder';
@@ -31,6 +32,8 @@ describe('MixinSignatureValidator', () => {
     let signatureValidator: TestSignatureValidatorContract;
     let testWallet: WalletContract;
     let testValidator: ValidatorContract;
+    let maliciousWallet: TestStaticCallReceiverContract;
+    let maliciousValidator: TestStaticCallReceiverContract;
     let signerAddress: string;
     let signerPrivateKey: Buffer;
     let notSignerAddress: string;
@@ -65,6 +68,11 @@ describe('MixinSignatureValidator', () => {
             txDefaults,
             signerAddress,
         );
+        maliciousWallet = maliciousValidator = await TestStaticCallReceiverContract.deployFrom0xArtifactAsync(
+            artifacts.TestStaticCallReceiver,
+            provider,
+            txDefaults,
+        );
         signatureValidatorLogDecoder = new LogDecoder(web3Wrapper);
         await web3Wrapper.awaitTransactionSuccessAsync(
             await signatureValidator.setSignatureValidatorApproval.sendTransactionAsync(testValidator.address, true, {
@@ -72,6 +80,16 @@ describe('MixinSignatureValidator', () => {
             }),
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
+        await web3Wrapper.awaitTransactionSuccessAsync(
+            await signatureValidator.setSignatureValidatorApproval.sendTransactionAsync(
+                maliciousValidator.address,
+                true,
+                {
+                    from: signerAddress,
+                },
+            ),
+            constants.AWAIT_TRANSACTION_MINED_MS,
+        );
 
         const defaultOrderParams = {
             ...constants.STATIC_ORDER_PARAMS,
@@ -263,32 +281,6 @@ describe('MixinSignatureValidator', () => {
             expect(isValidSignature).to.be.false();
         });
 
-        it('should return true when SignatureType=Caller and signer is caller', async () => {
-            const signature = ethUtil.toBuffer(`0x${SignatureType.Caller}`);
-            const signatureHex = ethUtil.bufferToHex(signature);
-            const orderHashHex = orderHashUtils.getOrderHashHex(signedOrder);
-            const isValidSignature = await signatureValidator.publicIsValidSignature.callAsync(
-                orderHashHex,
-                signerAddress,
-                signatureHex,
-                { from: signerAddress },
-            );
-            expect(isValidSignature).to.be.true();
-        });
-
-        it('should return false when SignatureType=Caller and signer is not caller', async () => {
-            const signature = ethUtil.toBuffer(`0x${SignatureType.Caller}`);
-            const signatureHex = ethUtil.bufferToHex(signature);
-            const orderHashHex = orderHashUtils.getOrderHashHex(signedOrder);
-            const isValidSignature = await signatureValidator.publicIsValidSignature.callAsync(
-                orderHashHex,
-                signerAddress,
-                signatureHex,
-                { from: notSignerAddress },
-            );
-            expect(isValidSignature).to.be.false();
-        });
-
         it('should return true when SignatureType=Wallet and signature is valid', async () => {
             // Create EIP712 signature
             const orderHashHex = orderHashUtils.getOrderHashHex(signedOrder);
@@ -334,6 +326,29 @@ describe('MixinSignatureValidator', () => {
             expect(isValidSignature).to.be.false();
         });
 
+        it('should revert when `isValidSignature` attempts to update state and SignatureType=Wallet', async () => {
+            // Create EIP712 signature
+            const orderHashHex = orderHashUtils.getOrderHashHex(signedOrder);
+            const orderHashBuffer = ethUtil.toBuffer(orderHashHex);
+            const ecSignature = ethUtil.ecsign(orderHashBuffer, signerPrivateKey);
+            // Create 0x signature from EIP712 signature
+            const signature = Buffer.concat([
+                ethUtil.toBuffer(ecSignature.v),
+                ecSignature.r,
+                ecSignature.s,
+                ethUtil.toBuffer(`0x${SignatureType.Wallet}`),
+            ]);
+            const signatureHex = ethUtil.bufferToHex(signature);
+            await expectContractCallFailed(
+                signatureValidator.publicIsValidSignature.callAsync(
+                    orderHashHex,
+                    maliciousWallet.address,
+                    signatureHex,
+                ),
+                RevertReason.WalletError,
+            );
+        });
+
         it('should return true when SignatureType=Validator, signature is valid and validator is approved', async () => {
             const validatorAddress = ethUtil.toBuffer(`${testValidator.address}`);
             const signatureType = ethUtil.toBuffer(`0x${SignatureType.Validator}`);
@@ -364,6 +379,17 @@ describe('MixinSignatureValidator', () => {
             expect(isValidSignature).to.be.false();
         });
 
+        it('should revert when `isValidSignature` attempts to update state and SignatureType=Validator', async () => {
+            const validatorAddress = ethUtil.toBuffer(`${maliciousValidator.address}`);
+            const signatureType = ethUtil.toBuffer(`0x${SignatureType.Validator}`);
+            const signature = Buffer.concat([validatorAddress, signatureType]);
+            const signatureHex = ethUtil.bufferToHex(signature);
+            const orderHashHex = orderHashUtils.getOrderHashHex(signedOrder);
+            await expectContractCallFailed(
+                signatureValidator.publicIsValidSignature.callAsync(orderHashHex, signerAddress, signatureHex),
+                RevertReason.ValidatorError,
+            );
+        });
         it('should return false when SignatureType=Validator, signature is valid and validator is not approved', async () => {
             // Set approval of signature validator to false
             await web3Wrapper.awaitTransactionSuccessAsync(
@@ -388,53 +414,6 @@ describe('MixinSignatureValidator', () => {
             expect(isValidSignature).to.be.false();
         });
 
-        it('should return true when SignatureType=Trezor and signature is valid', async () => {
-            // Create Trezor signature
-            const orderHashHex = orderHashUtils.getOrderHashHex(signedOrder);
-            const orderHashWithTrezorPrefixHex = signatureUtils.addSignedMessagePrefix(orderHashHex, SignerType.Trezor);
-            const orderHashWithTrezorPrefixBuffer = ethUtil.toBuffer(orderHashWithTrezorPrefixHex);
-            const ecSignature = ethUtil.ecsign(orderHashWithTrezorPrefixBuffer, signerPrivateKey);
-            // Create 0x signature from Trezor signature
-            const signature = Buffer.concat([
-                ethUtil.toBuffer(ecSignature.v),
-                ecSignature.r,
-                ecSignature.s,
-                ethUtil.toBuffer(`0x${SignatureType.Trezor}`),
-            ]);
-            const signatureHex = ethUtil.bufferToHex(signature);
-            // Validate signature
-            const isValidSignature = await signatureValidator.publicIsValidSignature.callAsync(
-                orderHashHex,
-                signerAddress,
-                signatureHex,
-            );
-            expect(isValidSignature).to.be.true();
-        });
-
-        it('should return false when SignatureType=Trezor and signature is invalid', async () => {
-            // Create Trezor signature
-            const orderHashHex = orderHashUtils.getOrderHashHex(signedOrder);
-            const orderHashWithTrezorPrefixHex = signatureUtils.addSignedMessagePrefix(orderHashHex, SignerType.Trezor);
-            const orderHashWithTrezorPrefixBuffer = ethUtil.toBuffer(orderHashWithTrezorPrefixHex);
-            const ecSignature = ethUtil.ecsign(orderHashWithTrezorPrefixBuffer, signerPrivateKey);
-            // Create 0x signature from Trezor signature
-            const signature = Buffer.concat([
-                ethUtil.toBuffer(ecSignature.v),
-                ecSignature.r,
-                ecSignature.s,
-                ethUtil.toBuffer(`0x${SignatureType.Trezor}`),
-            ]);
-            const signatureHex = ethUtil.bufferToHex(signature);
-            // Validate signature.
-            // This will fail because `signerAddress` signed the message, but we're passing in `notSignerAddress`
-            const isValidSignature = await signatureValidator.publicIsValidSignature.callAsync(
-                orderHashHex,
-                notSignerAddress,
-                signatureHex,
-            );
-            expect(isValidSignature).to.be.false();
-        });
-
         it('should return true when SignatureType=Presigned and signer has presigned hash', async () => {
             // Presign hash
             const orderHashHex = orderHashUtils.getOrderHashHex(signedOrder);
@@ -468,6 +447,42 @@ describe('MixinSignatureValidator', () => {
             );
             expect(isValidSignature).to.be.false();
         });
+
+        it('should return true when message was signed by a Trezor One (firmware version 1.6.2)', async () => {
+            // messageHash translates to 0x2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b
+            const messageHash = ethUtil.bufferToHex(ethUtil.toBuffer('++++++++++++++++++++++++++++++++'));
+            const signer = '0xc28b145f10f0bcf0fc000e778615f8fd73490bad';
+            const v = ethUtil.toBuffer('0x1c');
+            const r = ethUtil.toBuffer('0x7b888b596ccf87f0bacab0dcb483124973f7420f169b4824d7a12534ac1e9832');
+            const s = ethUtil.toBuffer('0x0c8e14f7edc01459e13965f1da56e0c23ed11e2cca932571eee1292178f90424');
+            const trezorSignatureType = ethUtil.toBuffer(`0x${SignatureType.EthSign}`);
+            const signature = Buffer.concat([v, r, s, trezorSignatureType]);
+            const signatureHex = ethUtil.bufferToHex(signature);
+            const isValidSignature = await signatureValidator.publicIsValidSignature.callAsync(
+                messageHash,
+                signer,
+                signatureHex,
+            );
+            expect(isValidSignature).to.be.true();
+        });
+
+        it('should return true when message was signed by a Trezor Model T (firmware version 2.0.7)', async () => {
+            // messageHash translates to 0x2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b
+            const messageHash = ethUtil.bufferToHex(ethUtil.toBuffer('++++++++++++++++++++++++++++++++'));
+            const signer = '0x98ce6d9345e8ffa7d99ee0822272fae9d2c0e895';
+            const v = ethUtil.toBuffer('0x1c');
+            const r = ethUtil.toBuffer('0x423b71062c327f0ec4fe199b8da0f34185e59b4c1cb4cc23df86cac4a601fb3f');
+            const s = ethUtil.toBuffer('0x53810d6591b5348b7ee08ee812c874b0fdfb942c9849d59512c90e295221091f');
+            const trezorSignatureType = ethUtil.toBuffer(`0x${SignatureType.EthSign}`);
+            const signature = Buffer.concat([v, r, s, trezorSignatureType]);
+            const signatureHex = ethUtil.bufferToHex(signature);
+            const isValidSignature = await signatureValidator.publicIsValidSignature.callAsync(
+                messageHash,
+                signer,
+                signatureHex,
+            );
+            expect(isValidSignature).to.be.true();
+        });
     });
 
     describe('setSignatureValidatorApproval', () => {
diff --git a/packages/contracts/test/exchange/wrapper.ts b/packages/contracts/test/exchange/wrapper.ts
index d48441dca..aadb5ab59 100644
--- a/packages/contracts/test/exchange/wrapper.ts
+++ b/packages/contracts/test/exchange/wrapper.ts
@@ -11,6 +11,7 @@ import { DummyERC721TokenContract } from '../../generated_contract_wrappers/dumm
 import { ERC20ProxyContract } from '../../generated_contract_wrappers/erc20_proxy';
 import { ERC721ProxyContract } from '../../generated_contract_wrappers/erc721_proxy';
 import { ExchangeContract } from '../../generated_contract_wrappers/exchange';
+import { ReentrantERC20TokenContract } from '../../generated_contract_wrappers/reentrant_erc20_token';
 import { artifacts } from '../utils/artifacts';
 import { expectTransactionFailedAsync } from '../utils/assertions';
 import { getLatestBlockTimestampAsync, increaseTimeAndMineBlockAsync } from '../utils/block_timestamp';
@@ -40,6 +41,7 @@ describe('Exchange wrappers', () => {
     let exchange: ExchangeContract;
     let erc20Proxy: ERC20ProxyContract;
     let erc721Proxy: ERC721ProxyContract;
+    let reentrantErc20Token: ReentrantERC20TokenContract;
 
     let exchangeWrapper: ExchangeWrapper;
     let erc20Wrapper: ERC20Wrapper;
@@ -104,6 +106,13 @@ describe('Exchange wrappers', () => {
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
 
+        reentrantErc20Token = await ReentrantERC20TokenContract.deployFrom0xArtifactAsync(
+            artifacts.ReentrantERC20Token,
+            provider,
+            txDefaults,
+            exchange.address,
+        );
+
         defaultMakerAssetAddress = erc20TokenA.address;
         defaultTakerAssetAddress = erc20TokenB.address;
 
@@ -126,6 +135,26 @@ describe('Exchange wrappers', () => {
         await blockchainLifecycle.revertAsync();
     });
     describe('fillOrKillOrder', () => {
+        const reentrancyTest = (functionNames: string[]) => {
+            _.forEach(functionNames, async (functionName: string, functionId: number) => {
+                const description = `should not allow fillOrKillOrder to reenter the Exchange contract via ${functionName}`;
+                it(description, async () => {
+                    const signedOrder = await orderFactory.newSignedOrderAsync({
+                        makerAssetData: assetDataUtils.encodeERC20AssetData(reentrantErc20Token.address),
+                    });
+                    await web3Wrapper.awaitTransactionSuccessAsync(
+                        await reentrantErc20Token.setCurrentFunction.sendTransactionAsync(functionId),
+                        constants.AWAIT_TRANSACTION_MINED_MS,
+                    );
+                    await expectTransactionFailedAsync(
+                        exchangeWrapper.fillOrKillOrderAsync(signedOrder, takerAddress),
+                        RevertReason.TransferFailed,
+                    );
+                });
+            });
+        };
+        describe('fillOrKillOrder reentrancy tests', () => reentrancyTest(constants.FUNCTIONS_WITH_MUTEX));
+
         it('should transfer the correct amounts', async () => {
             const signedOrder = await orderFactory.newSignedOrderAsync({
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 18),
@@ -197,6 +226,25 @@ describe('Exchange wrappers', () => {
     });
 
     describe('fillOrderNoThrow', () => {
+        const reentrancyTest = (functionNames: string[]) => {
+            _.forEach(functionNames, async (functionName: string, functionId: number) => {
+                const description = `should not allow fillOrderNoThrow to reenter the Exchange contract via ${functionName}`;
+                it(description, async () => {
+                    const signedOrder = await orderFactory.newSignedOrderAsync({
+                        makerAssetData: assetDataUtils.encodeERC20AssetData(reentrantErc20Token.address),
+                    });
+                    await web3Wrapper.awaitTransactionSuccessAsync(
+                        await reentrantErc20Token.setCurrentFunction.sendTransactionAsync(functionId),
+                        constants.AWAIT_TRANSACTION_MINED_MS,
+                    );
+                    await exchangeWrapper.fillOrderNoThrowAsync(signedOrder, takerAddress);
+                    const newBalances = await erc20Wrapper.getBalancesAsync();
+                    expect(erc20Balances).to.deep.equal(newBalances);
+                });
+            });
+        };
+        describe('fillOrderNoThrow reentrancy tests', () => reentrancyTest(constants.FUNCTIONS_WITH_MUTEX));
+
         it('should transfer the correct amounts', async () => {
             const signedOrder = await orderFactory.newSignedOrderAsync({
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(100), 18),
@@ -397,6 +445,26 @@ describe('Exchange wrappers', () => {
         });
 
         describe('batchFillOrders', () => {
+            const reentrancyTest = (functionNames: string[]) => {
+                _.forEach(functionNames, async (functionName: string, functionId: number) => {
+                    const description = `should not allow batchFillOrders to reenter the Exchange contract via ${functionName}`;
+                    it(description, async () => {
+                        const signedOrder = await orderFactory.newSignedOrderAsync({
+                            makerAssetData: assetDataUtils.encodeERC20AssetData(reentrantErc20Token.address),
+                        });
+                        await web3Wrapper.awaitTransactionSuccessAsync(
+                            await reentrantErc20Token.setCurrentFunction.sendTransactionAsync(functionId),
+                            constants.AWAIT_TRANSACTION_MINED_MS,
+                        );
+                        await expectTransactionFailedAsync(
+                            exchangeWrapper.batchFillOrdersAsync([signedOrder], takerAddress),
+                            RevertReason.TransferFailed,
+                        );
+                    });
+                });
+            };
+            describe('batchFillOrders reentrancy tests', () => reentrancyTest(constants.FUNCTIONS_WITH_MUTEX));
+
             it('should transfer the correct amounts', async () => {
                 const takerAssetFillAmounts: BigNumber[] = [];
                 const makerAssetAddress = erc20TokenA.address;
@@ -446,6 +514,26 @@ describe('Exchange wrappers', () => {
         });
 
         describe('batchFillOrKillOrders', () => {
+            const reentrancyTest = (functionNames: string[]) => {
+                _.forEach(functionNames, async (functionName: string, functionId: number) => {
+                    const description = `should not allow batchFillOrKillOrders to reenter the Exchange contract via ${functionName}`;
+                    it(description, async () => {
+                        const signedOrder = await orderFactory.newSignedOrderAsync({
+                            makerAssetData: assetDataUtils.encodeERC20AssetData(reentrantErc20Token.address),
+                        });
+                        await web3Wrapper.awaitTransactionSuccessAsync(
+                            await reentrantErc20Token.setCurrentFunction.sendTransactionAsync(functionId),
+                            constants.AWAIT_TRANSACTION_MINED_MS,
+                        );
+                        await expectTransactionFailedAsync(
+                            exchangeWrapper.batchFillOrKillOrdersAsync([signedOrder], takerAddress),
+                            RevertReason.TransferFailed,
+                        );
+                    });
+                });
+            };
+            describe('batchFillOrKillOrders reentrancy tests', () => reentrancyTest(constants.FUNCTIONS_WITH_MUTEX));
+
             it('should transfer the correct amounts', async () => {
                 const takerAssetFillAmounts: BigNumber[] = [];
                 const makerAssetAddress = erc20TokenA.address;
@@ -512,6 +600,25 @@ describe('Exchange wrappers', () => {
         });
 
         describe('batchFillOrdersNoThrow', async () => {
+            const reentrancyTest = (functionNames: string[]) => {
+                _.forEach(functionNames, async (functionName: string, functionId: number) => {
+                    const description = `should not allow batchFillOrdersNoThrow to reenter the Exchange contract via ${functionName}`;
+                    it(description, async () => {
+                        const signedOrder = await orderFactory.newSignedOrderAsync({
+                            makerAssetData: assetDataUtils.encodeERC20AssetData(reentrantErc20Token.address),
+                        });
+                        await web3Wrapper.awaitTransactionSuccessAsync(
+                            await reentrantErc20Token.setCurrentFunction.sendTransactionAsync(functionId),
+                            constants.AWAIT_TRANSACTION_MINED_MS,
+                        );
+                        await exchangeWrapper.batchFillOrdersNoThrowAsync([signedOrder], takerAddress);
+                        const newBalances = await erc20Wrapper.getBalancesAsync();
+                        expect(erc20Balances).to.deep.equal(newBalances);
+                    });
+                });
+            };
+            describe('batchFillOrdersNoThrow reentrancy tests', () => reentrancyTest(constants.FUNCTIONS_WITH_MUTEX));
+
             it('should transfer the correct amounts', async () => {
                 const takerAssetFillAmounts: BigNumber[] = [];
                 const makerAssetAddress = erc20TokenA.address;
@@ -625,6 +732,28 @@ describe('Exchange wrappers', () => {
         });
 
         describe('marketSellOrders', () => {
+            const reentrancyTest = (functionNames: string[]) => {
+                _.forEach(functionNames, async (functionName: string, functionId: number) => {
+                    const description = `should not allow marketSellOrders to reenter the Exchange contract via ${functionName}`;
+                    it(description, async () => {
+                        const signedOrder = await orderFactory.newSignedOrderAsync({
+                            makerAssetData: assetDataUtils.encodeERC20AssetData(reentrantErc20Token.address),
+                        });
+                        await web3Wrapper.awaitTransactionSuccessAsync(
+                            await reentrantErc20Token.setCurrentFunction.sendTransactionAsync(functionId),
+                            constants.AWAIT_TRANSACTION_MINED_MS,
+                        );
+                        await expectTransactionFailedAsync(
+                            exchangeWrapper.marketSellOrdersAsync([signedOrder], takerAddress, {
+                                takerAssetFillAmount: signedOrder.takerAssetAmount,
+                            }),
+                            RevertReason.TransferFailed,
+                        );
+                    });
+                });
+            };
+            describe('marketSellOrders reentrancy tests', () => reentrancyTest(constants.FUNCTIONS_WITH_MUTEX));
+
             it('should stop when the entire takerAssetFillAmount is filled', async () => {
                 const takerAssetFillAmount = signedOrders[0].takerAssetAmount.plus(
                     signedOrders[1].takerAssetAmount.div(2),
@@ -717,6 +846,27 @@ describe('Exchange wrappers', () => {
         });
 
         describe('marketSellOrdersNoThrow', () => {
+            const reentrancyTest = (functionNames: string[]) => {
+                _.forEach(functionNames, async (functionName: string, functionId: number) => {
+                    const description = `should not allow marketSellOrdersNoThrow to reenter the Exchange contract via ${functionName}`;
+                    it(description, async () => {
+                        const signedOrder = await orderFactory.newSignedOrderAsync({
+                            makerAssetData: assetDataUtils.encodeERC20AssetData(reentrantErc20Token.address),
+                        });
+                        await web3Wrapper.awaitTransactionSuccessAsync(
+                            await reentrantErc20Token.setCurrentFunction.sendTransactionAsync(functionId),
+                            constants.AWAIT_TRANSACTION_MINED_MS,
+                        );
+                        await exchangeWrapper.marketSellOrdersNoThrowAsync([signedOrder], takerAddress, {
+                            takerAssetFillAmount: signedOrder.takerAssetAmount,
+                        });
+                        const newBalances = await erc20Wrapper.getBalancesAsync();
+                        expect(erc20Balances).to.deep.equal(newBalances);
+                    });
+                });
+            };
+            describe('marketSellOrdersNoThrow reentrancy tests', () => reentrancyTest(constants.FUNCTIONS_WITH_MUTEX));
+
             it('should stop when the entire takerAssetFillAmount is filled', async () => {
                 const takerAssetFillAmount = signedOrders[0].takerAssetAmount.plus(
                     signedOrders[1].takerAssetAmount.div(2),
@@ -843,6 +993,28 @@ describe('Exchange wrappers', () => {
         });
 
         describe('marketBuyOrders', () => {
+            const reentrancyTest = (functionNames: string[]) => {
+                _.forEach(functionNames, async (functionName: string, functionId: number) => {
+                    const description = `should not allow marketBuyOrders to reenter the Exchange contract via ${functionName}`;
+                    it(description, async () => {
+                        const signedOrder = await orderFactory.newSignedOrderAsync({
+                            makerAssetData: assetDataUtils.encodeERC20AssetData(reentrantErc20Token.address),
+                        });
+                        await web3Wrapper.awaitTransactionSuccessAsync(
+                            await reentrantErc20Token.setCurrentFunction.sendTransactionAsync(functionId),
+                            constants.AWAIT_TRANSACTION_MINED_MS,
+                        );
+                        await expectTransactionFailedAsync(
+                            exchangeWrapper.marketBuyOrdersAsync([signedOrder], takerAddress, {
+                                makerAssetFillAmount: signedOrder.makerAssetAmount,
+                            }),
+                            RevertReason.TransferFailed,
+                        );
+                    });
+                });
+            };
+            describe('marketBuyOrders reentrancy tests', () => reentrancyTest(constants.FUNCTIONS_WITH_MUTEX));
+
             it('should stop when the entire makerAssetFillAmount is filled', async () => {
                 const makerAssetFillAmount = signedOrders[0].makerAssetAmount.plus(
                     signedOrders[1].makerAssetAmount.div(2),
@@ -933,6 +1105,27 @@ describe('Exchange wrappers', () => {
         });
 
         describe('marketBuyOrdersNoThrow', () => {
+            const reentrancyTest = (functionNames: string[]) => {
+                _.forEach(functionNames, async (functionName: string, functionId: number) => {
+                    const description = `should not allow marketBuyOrdersNoThrow to reenter the Exchange contract via ${functionName}`;
+                    it(description, async () => {
+                        const signedOrder = await orderFactory.newSignedOrderAsync({
+                            makerAssetData: assetDataUtils.encodeERC20AssetData(reentrantErc20Token.address),
+                        });
+                        await web3Wrapper.awaitTransactionSuccessAsync(
+                            await reentrantErc20Token.setCurrentFunction.sendTransactionAsync(functionId),
+                            constants.AWAIT_TRANSACTION_MINED_MS,
+                        );
+                        await exchangeWrapper.marketBuyOrdersNoThrowAsync([signedOrder], takerAddress, {
+                            makerAssetFillAmount: signedOrder.makerAssetAmount,
+                        });
+                        const newBalances = await erc20Wrapper.getBalancesAsync();
+                        expect(erc20Balances).to.deep.equal(newBalances);
+                    });
+                });
+            };
+            describe('marketBuyOrdersNoThrow reentrancy tests', () => reentrancyTest(constants.FUNCTIONS_WITH_MUTEX));
+
             it('should stop when the entire makerAssetFillAmount is filled', async () => {
                 const makerAssetFillAmount = signedOrders[0].makerAssetAmount.plus(
                     signedOrders[1].makerAssetAmount.div(2),
diff --git a/packages/contracts/test/utils/artifacts.ts b/packages/contracts/test/utils/artifacts.ts
index e8a7585ac..5ddb5cc7f 100644
--- a/packages/contracts/test/utils/artifacts.ts
+++ b/packages/contracts/test/utils/artifacts.ts
@@ -16,6 +16,7 @@ import * as MixinAuthorizable from '../../artifacts/MixinAuthorizable.json';
 import * as MultiSigWallet from '../../artifacts/MultiSigWallet.json';
 import * as MultiSigWalletWithTimeLock from '../../artifacts/MultiSigWalletWithTimeLock.json';
 import * as OrderValidator from '../../artifacts/OrderValidator.json';
+import * as ReentrantERC20Token from '../../artifacts/ReentrantERC20Token.json';
 import * as TestAssetProxyDispatcher from '../../artifacts/TestAssetProxyDispatcher.json';
 import * as TestAssetProxyOwner from '../../artifacts/TestAssetProxyOwner.json';
 import * as TestConstants from '../../artifacts/TestConstants.json';
@@ -23,6 +24,7 @@ import * as TestExchangeInternals from '../../artifacts/TestExchangeInternals.js
 import * as TestLibBytes from '../../artifacts/TestLibBytes.json';
 import * as TestLibs from '../../artifacts/TestLibs.json';
 import * as TestSignatureValidator from '../../artifacts/TestSignatureValidator.json';
+import * as TestStaticCallReceiver from '../../artifacts/TestStaticCallReceiver.json';
 import * as TokenRegistry from '../../artifacts/TokenRegistry.json';
 import * as Validator from '../../artifacts/Validator.json';
 import * as Wallet from '../../artifacts/Wallet.json';
@@ -48,6 +50,7 @@ export const artifacts = {
     MultiSigWallet: (MultiSigWallet as any) as ContractArtifact,
     MultiSigWalletWithTimeLock: (MultiSigWalletWithTimeLock as any) as ContractArtifact,
     OrderValidator: (OrderValidator as any) as ContractArtifact,
+    ReentrantERC20Token: (ReentrantERC20Token as any) as ContractArtifact,
     TestAssetProxyOwner: (TestAssetProxyOwner as any) as ContractArtifact,
     TestAssetProxyDispatcher: (TestAssetProxyDispatcher as any) as ContractArtifact,
     TestConstants: (TestConstants as any) as ContractArtifact,
@@ -55,6 +58,7 @@ export const artifacts = {
     TestLibs: (TestLibs as any) as ContractArtifact,
     TestExchangeInternals: (TestExchangeInternals as any) as ContractArtifact,
     TestSignatureValidator: (TestSignatureValidator as any) as ContractArtifact,
+    TestStaticCallReceiver: (TestStaticCallReceiver as any) as ContractArtifact,
     Validator: (Validator as any) as ContractArtifact,
     Wallet: (Wallet as any) as ContractArtifact,
     TokenRegistry: (TokenRegistry as any) as ContractArtifact,
diff --git a/packages/contracts/test/utils/constants.ts b/packages/contracts/test/utils/constants.ts
index 65eaee398..ee4378d2e 100644
--- a/packages/contracts/test/utils/constants.ts
+++ b/packages/contracts/test/utils/constants.ts
@@ -51,4 +51,16 @@ export const constants = {
     WORD_LENGTH: 32,
     ZERO_AMOUNT: new BigNumber(0),
     PERCENTAGE_DENOMINATOR: new BigNumber(10).pow(18),
+    FUNCTIONS_WITH_MUTEX: [
+        'FILL_ORDER',
+        'FILL_OR_KILL_ORDER',
+        'BATCH_FILL_ORDERS',
+        'BATCH_FILL_OR_KILL_ORDERS',
+        'MARKET_BUY_ORDERS',
+        'MARKET_SELL_ORDERS',
+        'MATCH_ORDERS',
+        'CANCEL_ORDER',
+        'CANCEL_ORDERS_UP_TO',
+        'SET_SIGNATURE_VALIDATOR_APPROVAL',
+    ],
 };
diff --git a/packages/contracts/test/utils/fill_order_combinatorial_utils.ts b/packages/contracts/test/utils/fill_order_combinatorial_utils.ts
index a9318571c..92d0f4003 100644
--- a/packages/contracts/test/utils/fill_order_combinatorial_utils.ts
+++ b/packages/contracts/test/utils/fill_order_combinatorial_utils.ts
@@ -467,17 +467,17 @@ export class FillOrderCombinatorialUtils {
             ? remainingTakerAmountToFill
             : alreadyFilledTakerAmount.add(takerAssetFillAmount);
 
-        const expFilledMakerAmount = orderUtils.getPartialAmount(
+        const expFilledMakerAmount = orderUtils.getPartialAmountFloor(
             expFilledTakerAmount,
             signedOrder.takerAssetAmount,
             signedOrder.makerAssetAmount,
         );
-        const expMakerFeePaid = orderUtils.getPartialAmount(
+        const expMakerFeePaid = orderUtils.getPartialAmountFloor(
             expFilledTakerAmount,
             signedOrder.takerAssetAmount,
             signedOrder.makerFee,
         );
-        const expTakerFeePaid = orderUtils.getPartialAmount(
+        const expTakerFeePaid = orderUtils.getPartialAmountFloor(
             expFilledTakerAmount,
             signedOrder.takerAssetAmount,
             signedOrder.takerFee,
@@ -668,7 +668,7 @@ export class FillOrderCombinatorialUtils {
         signedOrder: SignedOrder,
         takerAssetFillAmount: BigNumber,
     ): Promise<void> {
-        const makerAssetFillAmount = orderUtils.getPartialAmount(
+        const makerAssetFillAmount = orderUtils.getPartialAmountFloor(
             takerAssetFillAmount,
             signedOrder.takerAssetAmount,
             signedOrder.makerAssetAmount,
@@ -705,7 +705,7 @@ export class FillOrderCombinatorialUtils {
                 );
         }
 
-        const makerFee = orderUtils.getPartialAmount(
+        const makerFee = orderUtils.getPartialAmountFloor(
             takerAssetFillAmount,
             signedOrder.takerAssetAmount,
             signedOrder.makerFee,
@@ -829,7 +829,7 @@ export class FillOrderCombinatorialUtils {
                 );
         }
 
-        const takerFee = orderUtils.getPartialAmount(
+        const takerFee = orderUtils.getPartialAmountFloor(
             takerAssetFillAmount,
             signedOrder.takerAssetAmount,
             signedOrder.takerFee,
diff --git a/packages/contracts/test/utils/match_order_tester.ts b/packages/contracts/test/utils/match_order_tester.ts
index fa2eabc12..e0c55b834 100644
--- a/packages/contracts/test/utils/match_order_tester.ts
+++ b/packages/contracts/test/utils/match_order_tester.ts
@@ -4,11 +4,20 @@ import { BigNumber } from '@0xproject/utils';
 import * as chai from 'chai';
 import * as _ from 'lodash';
 
+import { TransactionReceiptWithDecodedLogs } from '../../../../node_modules/ethereum-types';
+
 import { chaiSetup } from './chai_setup';
 import { ERC20Wrapper } from './erc20_wrapper';
 import { ERC721Wrapper } from './erc721_wrapper';
 import { ExchangeWrapper } from './exchange_wrapper';
-import { ERC20BalancesByOwner, ERC721TokenIdsByOwner, TransferAmountsByMatchOrders as TransferAmounts } from './types';
+import {
+    ERC20BalancesByOwner,
+    ERC721TokenIdsByOwner,
+    OrderInfo,
+    OrderStatus,
+    TransferAmountsByMatchOrders as TransferAmounts,
+    TransferAmountsLoggedByMatchOrders as LoggedTransferAmounts,
+} from './types';
 
 chaiSetup.configure();
 const expect = chai.expect;
@@ -18,43 +27,107 @@ export class MatchOrderTester {
     private readonly _erc20Wrapper: ERC20Wrapper;
     private readonly _erc721Wrapper: ERC721Wrapper;
     private readonly _feeTokenAddress: string;
-
-    /// @dev Compares a pair of ERC20 balances and a pair of ERC721 token owners.
-    /// @param expectedNewERC20BalancesByOwner Expected ERC20 balances.
-    /// @param realERC20BalancesByOwner Actual ERC20 balances.
-    /// @param expectedNewERC721TokenIdsByOwner Expected ERC721 token owners.
-    /// @param realERC721TokenIdsByOwner Actual ERC20 token owners.
-    /// @return True only if ERC20 balances match and ERC721 token owners match.
-    private static _compareExpectedAndRealBalances(
-        expectedNewERC20BalancesByOwner: ERC20BalancesByOwner,
+    /// @dev Checks values from the logs produced by Exchange.matchOrders against the expected transfer amounts.
+    ///      Values include the amounts transferred from the left/right makers and taker, along with
+    ///      the fees paid on each matched order. These are also the return values of MatchOrders.
+    /// @param signedOrderLeft First matched order.
+    /// @param signedOrderRight Second matched order.
+    /// @param transactionReceipt Transaction receipt and logs produced by Exchange.matchOrders.
+    /// @param takerAddress Address of taker (account that called Exchange.matchOrders)
+    /// @param expectedTransferAmounts Expected amounts transferred as a result of order matching.
+    private static async _assertLogsAsync(
+        signedOrderLeft: SignedOrder,
+        signedOrderRight: SignedOrder,
+        transactionReceipt: TransactionReceiptWithDecodedLogs,
+        takerAddress: string,
+        expectedTransferAmounts: TransferAmounts,
+    ): Promise<void> {
+        // Should have two fill event logs -- one for each order.
+        const transactionFillLogs = _.filter(transactionReceipt.logs, ['event', 'Fill']);
+        expect(transactionFillLogs.length, 'Checking number of logs').to.be.equal(2);
+        // First log is for left fill
+        const leftLog = (transactionFillLogs[0] as any).args as LoggedTransferAmounts;
+        expect(leftLog.makerAddress, 'Checking logged maker address of left order').to.be.equal(
+            signedOrderLeft.makerAddress,
+        );
+        expect(leftLog.takerAddress, 'Checking logged taker address of right order').to.be.equal(takerAddress);
+        const amountBoughtByLeftMaker = new BigNumber(leftLog.takerAssetFilledAmount);
+        const amountSoldByLeftMaker = new BigNumber(leftLog.makerAssetFilledAmount);
+        const feePaidByLeftMaker = new BigNumber(leftLog.makerFeePaid);
+        const feePaidByTakerLeft = new BigNumber(leftLog.takerFeePaid);
+        // Second log is for right fill
+        const rightLog = (transactionFillLogs[1] as any).args as LoggedTransferAmounts;
+        expect(rightLog.makerAddress, 'Checking logged maker address of right order').to.be.equal(
+            signedOrderRight.makerAddress,
+        );
+        expect(rightLog.takerAddress, 'Checking loggerd taker address of right order').to.be.equal(takerAddress);
+        const amountBoughtByRightMaker = new BigNumber(rightLog.takerAssetFilledAmount);
+        const amountSoldByRightMaker = new BigNumber(rightLog.makerAssetFilledAmount);
+        const feePaidByRightMaker = new BigNumber(rightLog.makerFeePaid);
+        const feePaidByTakerRight = new BigNumber(rightLog.takerFeePaid);
+        // Derive amount received by taker
+        const amountReceivedByTaker = amountSoldByLeftMaker.sub(amountBoughtByRightMaker);
+        // Assert log values - left order
+        expect(amountBoughtByLeftMaker, 'Checking logged amount bought by left maker').to.be.bignumber.equal(
+            expectedTransferAmounts.amountBoughtByLeftMaker,
+        );
+        expect(amountSoldByLeftMaker, 'Checking logged amount sold by left maker').to.be.bignumber.equal(
+            expectedTransferAmounts.amountSoldByLeftMaker,
+        );
+        expect(feePaidByLeftMaker, 'Checking logged fee paid by left maker').to.be.bignumber.equal(
+            expectedTransferAmounts.feePaidByLeftMaker,
+        );
+        expect(feePaidByTakerLeft, 'Checking logged fee paid on left order by taker').to.be.bignumber.equal(
+            expectedTransferAmounts.feePaidByTakerLeft,
+        );
+        // Assert log values - right order
+        expect(amountBoughtByRightMaker, 'Checking logged amount bought by right maker').to.be.bignumber.equal(
+            expectedTransferAmounts.amountBoughtByRightMaker,
+        );
+        expect(amountSoldByRightMaker, 'Checking logged amount sold by right maker').to.be.bignumber.equal(
+            expectedTransferAmounts.amountSoldByRightMaker,
+        );
+        expect(feePaidByRightMaker, 'Checking logged fee paid by right maker').to.be.bignumber.equal(
+            expectedTransferAmounts.feePaidByRightMaker,
+        );
+        expect(feePaidByTakerRight, 'Checking logged fee paid on right order by taker').to.be.bignumber.equal(
+            expectedTransferAmounts.feePaidByTakerRight,
+        );
+        // Assert derived amount received by taker
+        expect(amountReceivedByTaker, 'Checking logged amount received by taker').to.be.bignumber.equal(
+            expectedTransferAmounts.amountReceivedByTaker,
+        );
+    }
+    /// @dev Asserts all expected ERC20 and ERC721 account holdings match the real holdings.
+    /// @param expectedERC20BalancesByOwner Expected ERC20 balances.
+    /// @param realERC20BalancesByOwner Real ERC20 balances.
+    /// @param expectedERC721TokenIdsByOwner Expected ERC721 token owners.
+    /// @param realERC721TokenIdsByOwner Real ERC20 token owners.
+    private static async _assertAllKnownBalancesAsync(
+        expectedERC20BalancesByOwner: ERC20BalancesByOwner,
         realERC20BalancesByOwner: ERC20BalancesByOwner,
-        expectedNewERC721TokenIdsByOwner: ERC721TokenIdsByOwner,
+        expectedERC721TokenIdsByOwner: ERC721TokenIdsByOwner,
         realERC721TokenIdsByOwner: ERC721TokenIdsByOwner,
-    ): boolean {
+    ): Promise<void> {
         // ERC20 Balances
-        const doesErc20BalancesMatch = _.isEqual(expectedNewERC20BalancesByOwner, realERC20BalancesByOwner);
-        if (!doesErc20BalancesMatch) {
-            return false;
-        }
+        const areERC20BalancesEqual = _.isEqual(expectedERC20BalancesByOwner, realERC20BalancesByOwner);
+        expect(areERC20BalancesEqual, 'Checking all known ERC20 account balances').to.be.true();
         // ERC721 Token Ids
-        const sortedExpectedNewERC721TokenIdsByOwner = _.mapValues(
-            expectedNewERC721TokenIdsByOwner,
-            tokenIdsByOwner => {
-                _.mapValues(tokenIdsByOwner, tokenIds => {
-                    _.sortBy(tokenIds);
-                });
-            },
-        );
+        const sortedExpectedNewERC721TokenIdsByOwner = _.mapValues(expectedERC721TokenIdsByOwner, tokenIdsByOwner => {
+            _.mapValues(tokenIdsByOwner, tokenIds => {
+                _.sortBy(tokenIds);
+            });
+        });
         const sortedNewERC721TokenIdsByOwner = _.mapValues(realERC721TokenIdsByOwner, tokenIdsByOwner => {
             _.mapValues(tokenIdsByOwner, tokenIds => {
                 _.sortBy(tokenIds);
             });
         });
-        const doesErc721TokenIdsMatch = _.isEqual(
+        const areERC721TokenIdsEqual = _.isEqual(
             sortedExpectedNewERC721TokenIdsByOwner,
             sortedNewERC721TokenIdsByOwner,
         );
-        return doesErc721TokenIdsMatch;
+        expect(areERC721TokenIdsEqual, 'Checking all known ERC721 account balances').to.be.true();
     }
     /// @dev Constructs new MatchOrderTester.
     /// @param exchangeWrapper Used to call to the Exchange.
@@ -72,150 +145,199 @@ export class MatchOrderTester {
         this._erc721Wrapper = erc721Wrapper;
         this._feeTokenAddress = feeTokenAddress;
     }
-    /// @dev Matches two complementary orders and validates results.
-    ///      Validation either succeeds or throws.
+    /// @dev Matches two complementary orders and asserts results.
     /// @param signedOrderLeft First matched order.
     /// @param signedOrderRight Second matched order.
     /// @param takerAddress Address of taker (the address who matched the two orders)
     /// @param erc20BalancesByOwner Current ERC20 balances.
     /// @param erc721TokenIdsByOwner Current ERC721 token owners.
-    /// @param initialTakerAssetFilledAmountLeft Current amount the left order has been filled.
-    /// @param initialTakerAssetFilledAmountRight Current amount the right order has been filled.
+    /// @param expectedTransferAmounts Expected amounts transferred as a result of order matching.
+    /// @param initialLeftOrderFilledAmount How much left order has been filled, prior to matching orders.
+    /// @param initialRightOrderFilledAmount How much the right order has been filled, prior to matching orders.
     /// @return New ERC20 balances & ERC721 token owners.
-    public async matchOrdersAndVerifyBalancesAsync(
+    public async matchOrdersAndAssertEffectsAsync(
         signedOrderLeft: SignedOrder,
         signedOrderRight: SignedOrder,
         takerAddress: string,
         erc20BalancesByOwner: ERC20BalancesByOwner,
         erc721TokenIdsByOwner: ERC721TokenIdsByOwner,
-        initialTakerAssetFilledAmountLeft?: BigNumber,
-        initialTakerAssetFilledAmountRight?: BigNumber,
+        expectedTransferAmounts: TransferAmounts,
+        initialLeftOrderFilledAmount: BigNumber = new BigNumber(0),
+        initialRightOrderFilledAmount: BigNumber = new BigNumber(0),
     ): Promise<[ERC20BalancesByOwner, ERC721TokenIdsByOwner]> {
-        // Verify Left order preconditions
-        const orderTakerAssetFilledAmountLeft = await this._exchangeWrapper.getTakerAssetFilledAmountAsync(
-            orderHashUtils.getOrderHashHex(signedOrderLeft),
-        );
-        const expectedOrderFilledAmountLeft = initialTakerAssetFilledAmountLeft
-            ? initialTakerAssetFilledAmountLeft
-            : new BigNumber(0);
-        expect(expectedOrderFilledAmountLeft).to.be.bignumber.equal(orderTakerAssetFilledAmountLeft);
-        // Verify Right order preconditions
-        const orderTakerAssetFilledAmountRight = await this._exchangeWrapper.getTakerAssetFilledAmountAsync(
-            orderHashUtils.getOrderHashHex(signedOrderRight),
+        // Assert initial order states
+        await this._assertInitialOrderStatesAsync(
+            signedOrderLeft,
+            signedOrderRight,
+            initialLeftOrderFilledAmount,
+            initialRightOrderFilledAmount,
         );
-        const expectedOrderFilledAmountRight = initialTakerAssetFilledAmountRight
-            ? initialTakerAssetFilledAmountRight
-            : new BigNumber(0);
-        expect(expectedOrderFilledAmountRight).to.be.bignumber.equal(orderTakerAssetFilledAmountRight);
         // Match left & right orders
-        await this._exchangeWrapper.matchOrdersAsync(signedOrderLeft, signedOrderRight, takerAddress);
+        const transactionReceipt = await this._exchangeWrapper.matchOrdersAsync(
+            signedOrderLeft,
+            signedOrderRight,
+            takerAddress,
+        );
         const newERC20BalancesByOwner = await this._erc20Wrapper.getBalancesAsync();
         const newERC721TokenIdsByOwner = await this._erc721Wrapper.getBalancesAsync();
-        // Calculate expected balance changes
-        const expectedTransferAmounts = await this._calculateExpectedTransferAmountsAsync(
+        // Assert logs
+        await MatchOrderTester._assertLogsAsync(
             signedOrderLeft,
             signedOrderRight,
-            orderTakerAssetFilledAmountLeft,
-            orderTakerAssetFilledAmountRight,
+            transactionReceipt,
+            takerAddress,
+            expectedTransferAmounts,
         );
-        let expectedERC20BalancesByOwner: ERC20BalancesByOwner;
-        let expectedERC721TokenIdsByOwner: ERC721TokenIdsByOwner;
-        [expectedERC20BalancesByOwner, expectedERC721TokenIdsByOwner] = this._calculateExpectedBalances(
+        // Assert exchange state
+        await this._assertExchangeStateAsync(
             signedOrderLeft,
             signedOrderRight,
-            takerAddress,
-            erc20BalancesByOwner,
-            erc721TokenIdsByOwner,
+            initialLeftOrderFilledAmount,
+            initialRightOrderFilledAmount,
             expectedTransferAmounts,
         );
-        // Assert our expected balances are equal to the actual balances
-        const didExpectedBalancesMatchRealBalances = MatchOrderTester._compareExpectedAndRealBalances(
-            expectedERC20BalancesByOwner,
+        // Assert balances of makers, taker, and fee recipients
+        await this._assertBalancesAsync(
+            signedOrderLeft,
+            signedOrderRight,
+            erc20BalancesByOwner,
+            erc721TokenIdsByOwner,
             newERC20BalancesByOwner,
-            expectedERC721TokenIdsByOwner,
             newERC721TokenIdsByOwner,
+            expectedTransferAmounts,
+            takerAddress,
         );
-        expect(didExpectedBalancesMatchRealBalances).to.be.true();
         return [newERC20BalancesByOwner, newERC721TokenIdsByOwner];
     }
-    /// @dev Calculates expected transfer amounts between order makers, fee recipients, and
-    ///      the taker when two orders are matched.
+    /// @dev Asserts initial exchange state for the left and right orders.
+    /// @param signedOrderLeft First matched order.
+    /// @param signedOrderRight Second matched order.
+    /// @param expectedOrderFilledAmountLeft How much left order has been filled, prior to matching orders.
+    /// @param expectedOrderFilledAmountRight How much the right order has been filled, prior to matching orders.
+    private async _assertInitialOrderStatesAsync(
+        signedOrderLeft: SignedOrder,
+        signedOrderRight: SignedOrder,
+        expectedOrderFilledAmountLeft: BigNumber,
+        expectedOrderFilledAmountRight: BigNumber,
+    ): Promise<void> {
+        // Assert left order initial state
+        const orderTakerAssetFilledAmountLeft = await this._exchangeWrapper.getTakerAssetFilledAmountAsync(
+            orderHashUtils.getOrderHashHex(signedOrderLeft),
+        );
+        expect(orderTakerAssetFilledAmountLeft, 'Checking inital state of left order').to.be.bignumber.equal(
+            expectedOrderFilledAmountLeft,
+        );
+        // Assert right order initial state
+        const orderTakerAssetFilledAmountRight = await this._exchangeWrapper.getTakerAssetFilledAmountAsync(
+            orderHashUtils.getOrderHashHex(signedOrderRight),
+        );
+        expect(orderTakerAssetFilledAmountRight, 'Checking inital state of right order').to.be.bignumber.equal(
+            expectedOrderFilledAmountRight,
+        );
+    }
+    /// @dev Asserts the exchange state against the expected amounts transferred by from matching orders.
     /// @param signedOrderLeft First matched order.
     /// @param signedOrderRight Second matched order.
-    /// @param orderTakerAssetFilledAmountLeft How much left order has been filled, prior to matching orders.
-    /// @param orderTakerAssetFilledAmountRight How much the right order has been filled, prior to matching orders.
+    /// @param initialLeftOrderFilledAmount How much left order has been filled, prior to matching orders.
+    /// @param initialRightOrderFilledAmount How much the right order has been filled, prior to matching orders.
     /// @return TransferAmounts A struct containing the expected transfer amounts.
-    private async _calculateExpectedTransferAmountsAsync(
+    private async _assertExchangeStateAsync(
         signedOrderLeft: SignedOrder,
         signedOrderRight: SignedOrder,
-        orderTakerAssetFilledAmountLeft: BigNumber,
-        orderTakerAssetFilledAmountRight: BigNumber,
-    ): Promise<TransferAmounts> {
+        initialLeftOrderFilledAmount: BigNumber,
+        initialRightOrderFilledAmount: BigNumber,
+        expectedTransferAmounts: TransferAmounts,
+    ): Promise<void> {
+        // Assert state for left order: amount bought by left maker
         let amountBoughtByLeftMaker = await this._exchangeWrapper.getTakerAssetFilledAmountAsync(
             orderHashUtils.getOrderHashHex(signedOrderLeft),
         );
-        amountBoughtByLeftMaker = amountBoughtByLeftMaker.minus(orderTakerAssetFilledAmountLeft);
-        const amountSoldByLeftMaker = amountBoughtByLeftMaker
-            .times(signedOrderLeft.makerAssetAmount)
-            .dividedToIntegerBy(signedOrderLeft.takerAssetAmount);
-        const amountReceivedByRightMaker = amountBoughtByLeftMaker
-            .times(signedOrderRight.takerAssetAmount)
-            .dividedToIntegerBy(signedOrderRight.makerAssetAmount);
-        const amountReceivedByTaker = amountSoldByLeftMaker.minus(amountReceivedByRightMaker);
+        amountBoughtByLeftMaker = amountBoughtByLeftMaker.minus(initialLeftOrderFilledAmount);
+        expect(amountBoughtByLeftMaker, 'Checking exchange state for left order').to.be.bignumber.equal(
+            expectedTransferAmounts.amountBoughtByLeftMaker,
+        );
+        // Assert state for right order: amount bought by right maker
         let amountBoughtByRightMaker = await this._exchangeWrapper.getTakerAssetFilledAmountAsync(
             orderHashUtils.getOrderHashHex(signedOrderRight),
         );
-        amountBoughtByRightMaker = amountBoughtByRightMaker.minus(orderTakerAssetFilledAmountRight);
-        const amountSoldByRightMaker = amountBoughtByRightMaker
-            .times(signedOrderRight.makerAssetAmount)
-            .dividedToIntegerBy(signedOrderRight.takerAssetAmount);
-        const amountReceivedByLeftMaker = amountSoldByRightMaker;
-        const feePaidByLeftMaker = signedOrderLeft.makerFee
-            .times(amountSoldByLeftMaker)
-            .dividedToIntegerBy(signedOrderLeft.makerAssetAmount);
-        const feePaidByRightMaker = signedOrderRight.makerFee
-            .times(amountSoldByRightMaker)
-            .dividedToIntegerBy(signedOrderRight.makerAssetAmount);
-        const feePaidByTakerLeft = signedOrderLeft.takerFee
-            .times(amountSoldByLeftMaker)
-            .dividedToIntegerBy(signedOrderLeft.makerAssetAmount);
-        const feePaidByTakerRight = signedOrderRight.takerFee
-            .times(amountSoldByRightMaker)
-            .dividedToIntegerBy(signedOrderRight.makerAssetAmount);
-        const totalFeePaidByTaker = feePaidByTakerLeft.add(feePaidByTakerRight);
-        const feeReceivedLeft = feePaidByLeftMaker.add(feePaidByTakerLeft);
-        const feeReceivedRight = feePaidByRightMaker.add(feePaidByTakerRight);
-        // Return values
-        const expectedTransferAmounts = {
-            // Left Maker
-            amountBoughtByLeftMaker,
-            amountSoldByLeftMaker,
-            amountReceivedByLeftMaker,
-            feePaidByLeftMaker,
-            // Right Maker
-            amountBoughtByRightMaker,
-            amountSoldByRightMaker,
-            amountReceivedByRightMaker,
-            feePaidByRightMaker,
-            // Taker
-            amountReceivedByTaker,
-            feePaidByTakerLeft,
-            feePaidByTakerRight,
-            totalFeePaidByTaker,
-            // Fee Recipients
-            feeReceivedLeft,
-            feeReceivedRight,
-        };
-        return expectedTransferAmounts;
+        amountBoughtByRightMaker = amountBoughtByRightMaker.minus(initialRightOrderFilledAmount);
+        expect(amountBoughtByRightMaker, 'Checking exchange state for right order').to.be.bignumber.equal(
+            expectedTransferAmounts.amountBoughtByRightMaker,
+        );
+        // Assert left order status
+        const maxAmountBoughtByLeftMaker = signedOrderLeft.takerAssetAmount.minus(initialLeftOrderFilledAmount);
+        const leftOrderInfo: OrderInfo = await this._exchangeWrapper.getOrderInfoAsync(signedOrderLeft);
+        const leftExpectedStatus = expectedTransferAmounts.amountBoughtByLeftMaker.equals(maxAmountBoughtByLeftMaker)
+            ? OrderStatus.FULLY_FILLED
+            : OrderStatus.FILLABLE;
+        expect(leftOrderInfo.orderStatus as OrderStatus, 'Checking exchange status for left order').to.be.equal(
+            leftExpectedStatus,
+        );
+        // Assert right order status
+        const maxAmountBoughtByRightMaker = signedOrderRight.takerAssetAmount.minus(initialRightOrderFilledAmount);
+        const rightOrderInfo: OrderInfo = await this._exchangeWrapper.getOrderInfoAsync(signedOrderRight);
+        const rightExpectedStatus = expectedTransferAmounts.amountBoughtByRightMaker.equals(maxAmountBoughtByRightMaker)
+            ? OrderStatus.FULLY_FILLED
+            : OrderStatus.FILLABLE;
+        expect(rightOrderInfo.orderStatus as OrderStatus, 'Checking exchange status for right order').to.be.equal(
+            rightExpectedStatus,
+        );
+    }
+    /// @dev Asserts account balances after matching orders.
+    /// @param signedOrderLeft First matched order.
+    /// @param signedOrderRight Second matched order.
+    /// @param initialERC20BalancesByOwner ERC20 balances prior to order matching.
+    /// @param initialERC721TokenIdsByOwner ERC721 token owners prior to order matching.
+    /// @param finalERC20BalancesByOwner ERC20 balances after order matching.
+    /// @param finalERC721TokenIdsByOwner ERC721 token owners after order matching.
+    /// @param expectedTransferAmounts Expected amounts transferred as a result of order matching.
+    /// @param takerAddress Address of taker (account that called Exchange.matchOrders).
+    private async _assertBalancesAsync(
+        signedOrderLeft: SignedOrder,
+        signedOrderRight: SignedOrder,
+        initialERC20BalancesByOwner: ERC20BalancesByOwner,
+        initialERC721TokenIdsByOwner: ERC721TokenIdsByOwner,
+        finalERC20BalancesByOwner: ERC20BalancesByOwner,
+        finalERC721TokenIdsByOwner: ERC721TokenIdsByOwner,
+        expectedTransferAmounts: TransferAmounts,
+        takerAddress: string,
+    ): Promise<void> {
+        let expectedERC20BalancesByOwner: ERC20BalancesByOwner;
+        let expectedERC721TokenIdsByOwner: ERC721TokenIdsByOwner;
+        [expectedERC20BalancesByOwner, expectedERC721TokenIdsByOwner] = this._calculateExpectedBalances(
+            signedOrderLeft,
+            signedOrderRight,
+            takerAddress,
+            initialERC20BalancesByOwner,
+            initialERC721TokenIdsByOwner,
+            expectedTransferAmounts,
+        );
+        // Assert balances of makers, taker, and fee recipients
+        await this._assertMakerTakerAndFeeRecipientBalancesAsync(
+            signedOrderLeft,
+            signedOrderRight,
+            expectedERC20BalancesByOwner,
+            finalERC20BalancesByOwner,
+            expectedERC721TokenIdsByOwner,
+            finalERC721TokenIdsByOwner,
+            takerAddress,
+        );
+        // Assert balances for all known accounts
+        await MatchOrderTester._assertAllKnownBalancesAsync(
+            expectedERC20BalancesByOwner,
+            finalERC20BalancesByOwner,
+            expectedERC721TokenIdsByOwner,
+            finalERC721TokenIdsByOwner,
+        );
     }
     /// @dev Calculates the expected balances of order makers, fee recipients, and the taker,
     ///      as a result of matching two orders.
-    /// @param signedOrderLeft First matched order.
+    /// @param signedOrderRight First matched order.
     /// @param signedOrderRight Second matched order.
     /// @param takerAddress Address of taker (the address who matched the two orders)
     /// @param erc20BalancesByOwner Current ERC20 balances.
     /// @param erc721TokenIdsByOwner Current ERC721 token owners.
-    /// @param expectedTransferAmounts A struct containing the expected transfer amounts.
+    /// @param expectedTransferAmounts Expected amounts transferred as a result of order matching.
     /// @return Expected ERC20 balances & ERC721 token owners after orders have been matched.
     private _calculateExpectedBalances(
         signedOrderLeft: SignedOrder,
@@ -247,7 +369,7 @@ export class MatchOrderTester {
             expectedNewERC20BalancesByOwner[makerAddressRight][
                 takerAssetAddressRight
             ] = expectedNewERC20BalancesByOwner[makerAddressRight][takerAssetAddressRight].add(
-                expectedTransferAmounts.amountReceivedByRightMaker,
+                expectedTransferAmounts.amountBoughtByRightMaker,
             );
             // Taker
             expectedNewERC20BalancesByOwner[takerAddress][makerAssetAddressLeft] = expectedNewERC20BalancesByOwner[
@@ -277,7 +399,7 @@ export class MatchOrderTester {
             // Left Maker
             expectedNewERC20BalancesByOwner[makerAddressLeft][takerAssetAddressLeft] = expectedNewERC20BalancesByOwner[
                 makerAddressLeft
-            ][takerAssetAddressLeft].add(expectedTransferAmounts.amountReceivedByLeftMaker);
+            ][takerAssetAddressLeft].add(expectedTransferAmounts.amountBoughtByLeftMaker);
             // Right Maker
             expectedNewERC20BalancesByOwner[makerAddressRight][
                 makerAssetAddressRight
@@ -307,20 +429,138 @@ export class MatchOrderTester {
         // Taker Fees
         expectedNewERC20BalancesByOwner[takerAddress][this._feeTokenAddress] = expectedNewERC20BalancesByOwner[
             takerAddress
-        ][this._feeTokenAddress].minus(expectedTransferAmounts.totalFeePaidByTaker);
+        ][this._feeTokenAddress].minus(
+            expectedTransferAmounts.feePaidByTakerLeft.add(expectedTransferAmounts.feePaidByTakerRight),
+        );
         // Left Fee Recipient Fees
         expectedNewERC20BalancesByOwner[feeRecipientAddressLeft][
             this._feeTokenAddress
         ] = expectedNewERC20BalancesByOwner[feeRecipientAddressLeft][this._feeTokenAddress].add(
-            expectedTransferAmounts.feeReceivedLeft,
+            expectedTransferAmounts.feePaidByLeftMaker.add(expectedTransferAmounts.feePaidByTakerLeft),
         );
         // Right Fee Recipient Fees
         expectedNewERC20BalancesByOwner[feeRecipientAddressRight][
             this._feeTokenAddress
         ] = expectedNewERC20BalancesByOwner[feeRecipientAddressRight][this._feeTokenAddress].add(
-            expectedTransferAmounts.feeReceivedRight,
+            expectedTransferAmounts.feePaidByRightMaker.add(expectedTransferAmounts.feePaidByTakerRight),
         );
 
         return [expectedNewERC20BalancesByOwner, expectedNewERC721TokenIdsByOwner];
     }
-}
+    /// @dev Asserts ERC20 account balances and ERC721 token holdings that result from order matching.
+    ///      Specifically checks balances of makers, taker and fee recipients.
+    /// @param signedOrderLeft First matched order.
+    /// @param signedOrderRight Second matched order.
+    /// @param expectedERC20BalancesByOwner Expected ERC20 balances.
+    /// @param realERC20BalancesByOwner Real ERC20 balances.
+    /// @param expectedERC721TokenIdsByOwner Expected ERC721 token owners.
+    /// @param realERC721TokenIdsByOwner Real ERC20 token owners.
+    /// @param takerAddress Address of taker (account that called Exchange.matchOrders).
+    private async _assertMakerTakerAndFeeRecipientBalancesAsync(
+        signedOrderLeft: SignedOrder,
+        signedOrderRight: SignedOrder,
+        expectedERC20BalancesByOwner: ERC20BalancesByOwner,
+        realERC20BalancesByOwner: ERC20BalancesByOwner,
+        expectedERC721TokenIdsByOwner: ERC721TokenIdsByOwner,
+        realERC721TokenIdsByOwner: ERC721TokenIdsByOwner,
+        takerAddress: string,
+    ): Promise<void> {
+        // Individual balance comparisons
+        const makerAssetProxyIdLeft = assetDataUtils.decodeAssetProxyId(signedOrderLeft.makerAssetData);
+        const makerERC20AssetDataLeft =
+            makerAssetProxyIdLeft === AssetProxyId.ERC20
+                ? assetDataUtils.decodeERC20AssetData(signedOrderLeft.makerAssetData)
+                : assetDataUtils.decodeERC721AssetData(signedOrderLeft.makerAssetData);
+        const makerAssetAddressLeft = makerERC20AssetDataLeft.tokenAddress;
+        const makerAssetProxyIdRight = assetDataUtils.decodeAssetProxyId(signedOrderRight.makerAssetData);
+        const makerERC20AssetDataRight =
+            makerAssetProxyIdRight === AssetProxyId.ERC20
+                ? assetDataUtils.decodeERC20AssetData(signedOrderRight.makerAssetData)
+                : assetDataUtils.decodeERC721AssetData(signedOrderRight.makerAssetData);
+        const makerAssetAddressRight = makerERC20AssetDataRight.tokenAddress;
+        if (makerAssetProxyIdLeft === AssetProxyId.ERC20) {
+            expect(
+                realERC20BalancesByOwner[signedOrderLeft.makerAddress][makerAssetAddressLeft],
+                'Checking left maker egress ERC20 account balance',
+            ).to.be.bignumber.equal(expectedERC20BalancesByOwner[signedOrderLeft.makerAddress][makerAssetAddressLeft]);
+            expect(
+                realERC20BalancesByOwner[signedOrderRight.makerAddress][makerAssetAddressLeft],
+                'Checking right maker ingress ERC20 account balance',
+            ).to.be.bignumber.equal(expectedERC20BalancesByOwner[signedOrderRight.makerAddress][makerAssetAddressLeft]);
+            expect(
+                realERC20BalancesByOwner[takerAddress][makerAssetAddressLeft],
+                'Checking taker ingress ERC20 account balance',
+            ).to.be.bignumber.equal(expectedERC20BalancesByOwner[takerAddress][makerAssetAddressLeft]);
+        } else if (makerAssetProxyIdLeft === AssetProxyId.ERC721) {
+            expect(
+                realERC721TokenIdsByOwner[signedOrderLeft.makerAddress][makerAssetAddressLeft].sort(),
+                'Checking left maker egress ERC721 account holdings',
+            ).to.be.deep.equal(
+                expectedERC721TokenIdsByOwner[signedOrderLeft.makerAddress][makerAssetAddressLeft].sort(),
+            );
+            expect(
+                realERC721TokenIdsByOwner[signedOrderRight.makerAddress][makerAssetAddressLeft].sort(),
+                'Checking right maker ERC721 account holdings',
+            ).to.be.deep.equal(
+                expectedERC721TokenIdsByOwner[signedOrderRight.makerAddress][makerAssetAddressLeft].sort(),
+            );
+            expect(
+                realERC721TokenIdsByOwner[takerAddress][makerAssetAddressLeft].sort(),
+                'Checking taker ingress ERC721 account holdings',
+            ).to.be.deep.equal(expectedERC721TokenIdsByOwner[takerAddress][makerAssetAddressLeft].sort());
+        } else {
+            throw new Error(`Unhandled Asset Proxy ID: ${makerAssetProxyIdLeft}`);
+        }
+        if (makerAssetProxyIdRight === AssetProxyId.ERC20) {
+            expect(
+                realERC20BalancesByOwner[signedOrderLeft.makerAddress][makerAssetAddressRight],
+                'Checking left maker ingress ERC20 account balance',
+            ).to.be.bignumber.equal(expectedERC20BalancesByOwner[signedOrderLeft.makerAddress][makerAssetAddressRight]);
+            expect(
+                realERC20BalancesByOwner[signedOrderRight.makerAddress][makerAssetAddressRight],
+                'Checking right maker egress ERC20 account balance',
+            ).to.be.bignumber.equal(
+                expectedERC20BalancesByOwner[signedOrderRight.makerAddress][makerAssetAddressRight],
+            );
+        } else if (makerAssetProxyIdRight === AssetProxyId.ERC721) {
+            expect(
+                realERC721TokenIdsByOwner[signedOrderLeft.makerAddress][makerAssetAddressRight].sort(),
+                'Checking left maker ingress ERC721 account holdings',
+            ).to.be.deep.equal(
+                expectedERC721TokenIdsByOwner[signedOrderLeft.makerAddress][makerAssetAddressRight].sort(),
+            );
+            expect(
+                realERC721TokenIdsByOwner[signedOrderRight.makerAddress][makerAssetAddressRight],
+                'Checking right maker agress ERC721 account holdings',
+            ).to.be.deep.equal(expectedERC721TokenIdsByOwner[signedOrderRight.makerAddress][makerAssetAddressRight]);
+        } else {
+            throw new Error(`Unhandled Asset Proxy ID: ${makerAssetProxyIdRight}`);
+        }
+        // Paid fees
+        expect(
+            realERC20BalancesByOwner[signedOrderLeft.makerAddress][this._feeTokenAddress],
+            'Checking left maker egress ERC20 account fees',
+        ).to.be.bignumber.equal(expectedERC20BalancesByOwner[signedOrderLeft.makerAddress][this._feeTokenAddress]);
+        expect(
+            realERC20BalancesByOwner[signedOrderRight.makerAddress][this._feeTokenAddress],
+            'Checking right maker egress ERC20 account fees',
+        ).to.be.bignumber.equal(expectedERC20BalancesByOwner[signedOrderRight.makerAddress][this._feeTokenAddress]);
+        expect(
+            realERC20BalancesByOwner[takerAddress][this._feeTokenAddress],
+            'Checking taker egress ERC20 account fees',
+        ).to.be.bignumber.equal(expectedERC20BalancesByOwner[takerAddress][this._feeTokenAddress]);
+        // Received fees
+        expect(
+            realERC20BalancesByOwner[signedOrderLeft.feeRecipientAddress][this._feeTokenAddress],
+            'Checking left fee recipient ingress ERC20 account fees',
+        ).to.be.bignumber.equal(
+            expectedERC20BalancesByOwner[signedOrderLeft.feeRecipientAddress][this._feeTokenAddress],
+        );
+        expect(
+            realERC20BalancesByOwner[signedOrderRight.feeRecipientAddress][this._feeTokenAddress],
+            'Checking right fee receipient ingress ERC20 account fees',
+        ).to.be.bignumber.equal(
+            expectedERC20BalancesByOwner[signedOrderRight.feeRecipientAddress][this._feeTokenAddress],
+        );
+    }
+} // tslint:disable-line:max-file-line-count
diff --git a/packages/contracts/test/utils/order_utils.ts b/packages/contracts/test/utils/order_utils.ts
index 019f6e74b..444e27c44 100644
--- a/packages/contracts/test/utils/order_utils.ts
+++ b/packages/contracts/test/utils/order_utils.ts
@@ -5,7 +5,7 @@ import { constants } from './constants';
 import { CancelOrder, MatchOrder } from './types';
 
 export const orderUtils = {
-    getPartialAmount(numerator: BigNumber, denominator: BigNumber, target: BigNumber): BigNumber {
+    getPartialAmountFloor(numerator: BigNumber, denominator: BigNumber, target: BigNumber): BigNumber {
         const partialAmount = numerator
             .mul(target)
             .div(denominator)
diff --git a/packages/contracts/test/utils/test_with_reference.ts b/packages/contracts/test/utils/test_with_reference.ts
index 599b1eed4..b80be4a6c 100644
--- a/packages/contracts/test/utils/test_with_reference.ts
+++ b/packages/contracts/test/utils/test_with_reference.ts
@@ -6,6 +6,34 @@ import { chaiSetup } from './chai_setup';
 chaiSetup.configure();
 const expect = chai.expect;
 
+class Value<T> {
+    public value: T;
+    constructor(value: T) {
+        this.value = value;
+    }
+}
+
+// tslint:disable-next-line: max-classes-per-file
+class ErrorMessage {
+    public error: string;
+    constructor(message: string) {
+        this.error = message;
+    }
+}
+
+type PromiseResult<T> = Value<T> | ErrorMessage;
+
+// TODO(albrow): This seems like a generic utility function that could exist in
+// lodash. We should replace it by a library implementation, or move it to our
+// own.
+async function evaluatePromise<T>(promise: Promise<T>): Promise<PromiseResult<T>> {
+    try {
+        return new Value<T>(await promise);
+    } catch (e) {
+        return new ErrorMessage(e.message);
+    }
+}
+
 export async function testWithReferenceFuncAsync<P0, R>(
     referenceFunc: (p0: P0) => Promise<R>,
     testFunc: (p0: P0) => Promise<R>,
@@ -64,39 +92,31 @@ export async function testWithReferenceFuncAsync(
     testFuncAsync: (...args: any[]) => Promise<any>,
     values: any[],
 ): Promise<void> {
-    let expectedResult: any;
-    let expectedErr: string | undefined;
-    try {
-        expectedResult = await referenceFuncAsync(...values);
-    } catch (e) {
-        expectedErr = e.message;
-    }
-    let actualResult: any | undefined;
-    try {
-        actualResult = await testFuncAsync(...values);
-        if (!_.isUndefined(expectedErr)) {
+    // Measure correct behaviour
+    const expected = await evaluatePromise(referenceFuncAsync(...values));
+
+    // Measure actual behaviour
+    const actual = await evaluatePromise(testFuncAsync(...values));
+
+    // Compare behaviour
+    if (expected instanceof ErrorMessage) {
+        // If we expected an error, check if the actual error message contains the
+        // expected error message.
+        if (!(actual instanceof ErrorMessage)) {
             throw new Error(
-                `Expected error containing ${expectedErr} but got no error\n\tTest case: ${_getTestCaseString(
+                `Expected error containing ${expected.error} but got no error\n\tTest case: ${_getTestCaseString(
                     referenceFuncAsync,
                     values,
                 )}`,
             );
         }
-    } catch (e) {
-        if (_.isUndefined(expectedErr)) {
-            throw new Error(`${e.message}\n\tTest case: ${_getTestCaseString(referenceFuncAsync, values)}`);
-        } else {
-            expect(e.message).to.contain(
-                expectedErr,
-                `${e.message}\n\tTest case: ${_getTestCaseString(referenceFuncAsync, values)}`,
-            );
-        }
-    }
-    if (!_.isUndefined(actualResult) && !_.isUndefined(expectedResult)) {
-        expect(actualResult).to.deep.equal(
-            expectedResult,
-            `Test case: ${_getTestCaseString(referenceFuncAsync, values)}`,
+        expect(actual.error).to.contain(
+            expected.error,
+            `${actual.error}\n\tTest case: ${_getTestCaseString(referenceFuncAsync, values)}`,
         );
+    } else {
+        // If we do not expect an error, compare actual and expected directly.
+        expect(actual).to.deep.equal(expected, `Test case ${_getTestCaseString(referenceFuncAsync, values)}`);
     }
 }
 
diff --git a/packages/contracts/test/utils/types.ts b/packages/contracts/test/utils/types.ts
index 481ee87d6..598fb5393 100644
--- a/packages/contracts/test/utils/types.ts
+++ b/packages/contracts/test/utils/types.ts
@@ -117,21 +117,24 @@ export interface TransferAmountsByMatchOrders {
     // Left Maker
     amountBoughtByLeftMaker: BigNumber;
     amountSoldByLeftMaker: BigNumber;
-    amountReceivedByLeftMaker: BigNumber;
     feePaidByLeftMaker: BigNumber;
     // Right Maker
     amountBoughtByRightMaker: BigNumber;
     amountSoldByRightMaker: BigNumber;
-    amountReceivedByRightMaker: BigNumber;
     feePaidByRightMaker: BigNumber;
     // Taker
     amountReceivedByTaker: BigNumber;
     feePaidByTakerLeft: BigNumber;
     feePaidByTakerRight: BigNumber;
-    totalFeePaidByTaker: BigNumber;
-    // Fee Recipients
-    feeReceivedLeft: BigNumber;
-    feeReceivedRight: BigNumber;
+}
+
+export interface TransferAmountsLoggedByMatchOrders {
+    makerAddress: string;
+    takerAddress: string;
+    makerAssetFilledAmount: string;
+    takerAssetFilledAmount: string;
+    makerFeePaid: string;
+    takerFeePaid: string;
 }
 
 export interface OrderInfo {
diff --git a/packages/contracts/test/utils_test/test_with_reference.ts b/packages/contracts/test/utils_test/test_with_reference.ts
new file mode 100644
index 000000000..8d633cd1f
--- /dev/null
+++ b/packages/contracts/test/utils_test/test_with_reference.ts
@@ -0,0 +1,63 @@
+import * as chai from 'chai';
+
+import { chaiSetup } from '../utils/chai_setup';
+import { testWithReferenceFuncAsync } from '../utils/test_with_reference';
+
+chaiSetup.configure();
+const expect = chai.expect;
+
+async function divAsync(x: number, y: number): Promise<number> {
+    if (y === 0) {
+        throw new Error('MathError: divide by zero');
+    }
+    return x / y;
+}
+
+// returns an async function that always returns the given value.
+function alwaysValueFunc(value: number): (x: number, y: number) => Promise<number> {
+    return async (x: number, y: number) => value;
+}
+
+// returns an async function which always throws/rejects with the given error
+// message.
+function alwaysFailFunc(errMessage: string): (x: number, y: number) => Promise<number> {
+    return async (x: number, y: number) => {
+        throw new Error(errMessage);
+    };
+}
+
+describe('testWithReferenceFuncAsync', () => {
+    it('passes when both succeed and actual === expected', async () => {
+        await testWithReferenceFuncAsync(alwaysValueFunc(0.5), divAsync, [1, 2]);
+    });
+
+    it('passes when both fail and actual error contains expected error', async () => {
+        await testWithReferenceFuncAsync(alwaysFailFunc('divide by zero'), divAsync, [1, 0]);
+    });
+
+    it('fails when both succeed and actual !== expected', async () => {
+        expect(testWithReferenceFuncAsync(alwaysValueFunc(3), divAsync, [1, 2])).to.be.rejectedWith(
+            'Test case {"x":1,"y":2}: expected { value: 0.5 } to deeply equal { value: 3 }',
+        );
+    });
+
+    it('fails when both fail and actual error does not contain expected error', async () => {
+        expect(
+            testWithReferenceFuncAsync(alwaysFailFunc('Unexpected math error'), divAsync, [1, 0]),
+        ).to.be.rejectedWith(
+            'MathError: divide by zero\n\tTest case: {"x":1,"y":0}: expected \'MathError: divide by zero\' to include \'Unexpected math error\'',
+        );
+    });
+
+    it('fails when referenceFunc succeeds and testFunc fails', async () => {
+        expect(testWithReferenceFuncAsync(alwaysValueFunc(0), divAsync, [1, 0])).to.be.rejectedWith(
+            'Test case {"x":1,"y":0}: expected { error: \'MathError: divide by zero\' } to deeply equal { value: 0 }',
+        );
+    });
+
+    it('fails when referenceFunc fails and testFunc succeeds', async () => {
+        expect(testWithReferenceFuncAsync(alwaysFailFunc('divide by zero'), divAsync, [1, 2])).to.be.rejectedWith(
+            'Expected error containing divide by zero but got no error\n\tTest case: {"x":1,"y":2}',
+        );
+    });
+});