Merge branch 'v2-prototype' of https://github.com/0xProject/0x-monorepo into feature/website/support-new-metamask

42 files changed, 2133 insertions, 585 deletions

diff --git a/packages/contracts/src/abstract/abstract_asset_wrapper.ts b/packages/contracts/src/abstract/abstract_asset_wrapper.ts
new file mode 100644
index 000000000..4b56a8502
--- /dev/null
+++ b/packages/contracts/src/abstract/abstract_asset_wrapper.ts
@@ -0,0 +1,3 @@
+export abstract class AbstractAssetWrapper {
+    public abstract getProxyId(): string;
+}
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol
index 7ca823d1f..b4780b52b 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC20Proxy.sol
@@ -20,24 +20,147 @@ pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "../../utils/LibBytes/LibBytes.sol";
-import "./MixinAssetProxy.sol";
+import "./interfaces/IAssetProxy.sol";
 import "./MixinAuthorizable.sol";
-import "./MixinERC20Transfer.sol";
 
 contract ERC20Proxy is
-    MixinAssetProxy,
-    MixinAuthorizable,
-    MixinERC20Transfer
+    IAssetProxy,
+    MixinAuthorizable
 {
     // Id of this proxy.
-    uint8 constant PROXY_ID = 1;
+    bytes4 constant PROXY_ID = bytes4(keccak256("ERC20Token(address)"));
+    
+    /// @dev Internal version of `transferFrom`.
+    /// @param assetData Encoded byte array.
+    /// @param from Address to transfer asset from.
+    /// @param to Address to transfer asset to.
+    /// @param amount Amount of asset to transfer.
+    function transferFrom(
+        bytes assetData,
+        address from,
+        address to,
+        uint256 amount
+    )
+        external
+    {
+        require(
+            authorized[msg.sender],
+            "SENDER_NOT_AUTHORIZED"
+        );
+
+        // `transferFrom`.
+        // The function is marked `external`, so no abi decodeding is done for
+        // us. Instead, we expect the `calldata` memory to contain the
+        // following:
+        //
+        // | Area     | Offset | Length  | Contents                            |
+        // |----------|--------|---------|-------------------------------------|
+        // | Header   | 0      | 4       | function selector                   |
+        // | Params   |        | 4 * 32  | function parameters:                |
+        // |          | 4      |         |   1. offset to assetData (*)        |
+        // |          | 36     |         |   2. from                           |
+        // |          | 68     |         |   3. to                             |
+        // |          | 100    |         |   4. amount                         |
+        // | Data     |        |         | assetData:                          |
+        // |          | 132    | 32      | assetData Length                    |
+        // |          | 164    | **      | assetData Contents                  |
+        //
+        // (*): offset is computed from start of function parameters, so offset
+        //      by an additional 4 bytes in the calldata.
+        //
+        // WARNING: The ABIv2 specification allows additional padding between
+        //          the Params and Data section. This will result in a larger
+        //          offset to assetData.
+        
+        // Asset data itself is encoded as follows:
+        //
+        // | Area     | Offset | Length  | Contents                            |
+        // |----------|--------|---------|-------------------------------------|
+        // | Header   | 0      | 4       | function selector                   |
+        // | Params   |        | 1 * 32  | function parameters:                |
+        // |          | 4      | 12 + 20 |   1. token address                  |
+        
+        // Transfer tokens.
+        // We do a raw call so we can check the success separate
+        // from the return data.
+        // We construct calldata for the `token.transferFrom` ABI.
+        // The layout of this calldata is in the table below.
+        // 
+        // | Area     | Offset | Length  | Contents                            |
+        // |----------|--------|---------|-------------------------------------|
+        // | Header   | 0      | 4       | function selector                   |
+        // | Params   |        | 3 * 32  | function parameters:                |
+        // |          | 4      |         |   1. from                           |
+        // |          | 36     |         |   2. to                             |
+        // |          | 68     |         |   3. amount                         |
+        
+        assembly {
+            /////// Token contract address ///////
+            // The token address is found as follows:
+            // * It is stored at offset 4 in `assetData` contents.
+            // * This is stored at offset 32 from `assetData`.
+            // * The offset to `assetData` from Params is stored at offset
+            //   4 in calldata.
+            // * The offset of Params in calldata is 4.
+            // So we read location 4 and add 32 + 4 + 4 to it.
+            let token := calldataload(add(calldataload(4), 40))
+            
+            /////// Setup Header Area ///////
+            // This area holds the 4-byte `transferFrom` selector.
+            // Any trailing data in transferFromSelector will be
+            // overwritten in the next `mstore` call.
+            mstore(0, 0x23b872dd00000000000000000000000000000000000000000000000000000000)
+            
+            /////// Setup Params Area ///////
+            // We copy the fields `from`, `to` and `amount` in bulk
+            // from our own calldata to the new calldata.
+            calldatacopy(4, 36, 96)
+
+            /////// Call `token.transferFrom` using the calldata ///////
+            let success := call(
+                gas,            // forward all gas
+                token,          // call address of token contract
+                0,              // don't send any ETH
+                0,              // pointer to start of input
+                100,            // length of input
+                0,              // write output over input
+                32              // output size should be 32 bytes
+            )
+
+            /////// Check return data. ///////
+            // If there is no return data, we assume the token incorrectly
+            // does not return a bool. In this case we expect it to revert
+            // on failure, which was handled above.
+            // If the token does return data, we require that it is a single
+            // nonzero 32 bytes value.
+            // So the transfer succeeded if the call succeeded and either
+            // returned nothing, or returned a non-zero 32 byte value. 
+            success := and(success, or(
+                iszero(returndatasize),
+                and(
+                    eq(returndatasize, 32),
+                    gt(mload(0), 0)
+                )
+            ))
+            if success {
+                return(0, 0)
+            }
+            
+            // Revert with `Error("TRANSFER_FAILED")`
+            mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000)
+            mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000)
+            mstore(64, 0x0000000f5452414e534645525f4641494c454400000000000000000000000000)
+            mstore(96, 0)
+            revert(0, 100)
+        }
+    }
 
     /// @dev Gets the proxy id associated with the proxy address.
     /// @return Proxy id.
     function getProxyId()
         external
         view
-        returns (uint8)
+        returns (bytes4)
     {
         return PROXY_ID;
     }
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol
index 7ff25aea3..8d7cea717 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/ERC721Proxy.sol
@@ -20,24 +20,187 @@ pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "../../utils/LibBytes/LibBytes.sol";
-import "./MixinAssetProxy.sol";
+import "./interfaces/IAssetProxy.sol";
 import "./MixinAuthorizable.sol";
-import "./MixinERC721Transfer.sol";
 
 contract ERC721Proxy is
-    MixinAssetProxy,
-    MixinAuthorizable,
-    MixinERC721Transfer
+    IAssetProxy,
+    MixinAuthorizable
 {
     // Id of this proxy.
-    uint8 constant PROXY_ID = 2;
+    bytes4 constant PROXY_ID = bytes4(keccak256("ERC721Token(address,uint256,bytes)"));
+
+    /// @dev Internal version of `transferFrom`.
+    /// @param assetData Encoded byte array.
+    /// @param from Address to transfer asset from.
+    /// @param to Address to transfer asset to.
+    /// @param amount Amount of asset to transfer.
+    function transferFrom(
+        bytes assetData,
+        address from,
+        address to,
+        uint256 amount
+    )
+        external
+    {
+        require(
+            authorized[msg.sender],
+            "SENDER_NOT_AUTHORIZED"
+        );
+    
+        // `transferFrom`.
+        // The function is marked `external`, so no abi decodeding is done for
+        // us. Instead, we expect the `calldata` memory to contain the
+        // following:
+        //
+        // | Area     | Offset | Length  | Contents                            |
+        // |----------|--------|---------|-------------------------------------|
+        // | Header   | 0      | 4       | function selector                   |
+        // | Params   |        | 4 * 32  | function parameters:                |
+        // |          | 4      |         |   1. offset to assetData (*)        |
+        // |          | 36     |         |   2. from                           |
+        // |          | 68     |         |   3. to                             |
+        // |          | 100    |         |   4. amount                         |
+        // | Data     |        |         | assetData:                          |
+        // |          | 132    | 32      | assetData Length                    |
+        // |          | 164    | **      | assetData Contents                  |
+        //
+        // (*): offset is computed from start of function parameters, so offset
+        //      by an additional 4 bytes in the calldata.
+        //
+        // WARNING: The ABIv2 specification allows additional padding between
+        //          the Params and Data section. This will result in a larger
+        //          offset to assetData.
+        
+        // Asset data itself is encoded as follows:
+        //
+        // | Area     | Offset | Length  | Contents                            |
+        // |----------|--------|---------|-------------------------------------|
+        // | Header   | 0      | 4       | function selector                   |
+        // | Params   |        | 3 * 32  | function parameters:                |
+        // |          | 4      | 12 + 20 |   1. token address                  |
+        // |          | 36     |         |   2. tokenId                        |
+        // |          | 68     |         |   3. offset to receiverData (*)     |
+        // | Data     |        |         | receiverData:                       |
+        // |          | 100    | 32      | receiverData Length                 |
+        // |          | 132    | **      | receiverData Contents               |
+        
+        // We construct calldata for the `token.safeTransferFrom` ABI.
+        // The layout of this calldata is in the table below.
+        // 
+        // | Area     | Offset | Length  | Contents                            |
+        // |----------|--------|---------|-------------------------------------|
+        // | Header   | 0      | 4       | function selector                   |
+        // | Params   |        | 4 * 32  | function parameters:                |
+        // |          | 4      |         |   1. from                           |
+        // |          | 36     |         |   2. to                             |
+        // |          | 68     |         |   3. tokenId                        |
+        // |          | 100    |         |   4. offset to receiverData (*)     |
+        // | Data     |        |         | receiverData:                       |
+        // |          | 132    | 32      | receiverData Length                 |
+        // |          | 164    | **      | receiverData Contents               |
+
+        assembly {
+            // There exists only 1 of each token.
+            // require(amount == 1, "INVALID_AMOUNT")
+            if sub(calldataload(100), 1) {
+                // Revert with `Error("INVALID_AMOUNT")`
+                mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000)
+                mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000)
+                mstore(64, 0x0000000e494e56414c49445f414d4f554e540000000000000000000000000000)
+                mstore(96, 0)
+                revert(0, 100)
+            }
+            
+            // Require assetData to be at least 132 bytes
+            let offset := calldataload(4)
+            if lt(calldataload(add(offset, 4)), 132) {
+                // Revert with `Error("LENGTH_GREATER_THAN_131_REQUIRED")`
+                mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000)
+                mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000)
+                mstore(64, 0x000000204c454e4754485f475245415445525f5448414e5f3133315f52455155)
+                mstore(96, 0x4952454400000000000000000000000000000000000000000000000000000000)
+                revert(0, 100)
+            }
+            
+            /////// Setup State ///////
+            // `cdStart` is the start of the calldata for
+            // `token.safeTransferFrom` (equal to free memory ptr).
+            let cdStart := mload(64)
+            // `dataAreaLength` is the total number of words
+            // needed to store `receiverData`
+            // As-per the ABI spec, this value is padded up to
+            // the nearest multiple of 32,
+            // and includes 32-bytes for length.
+            // It's calculated as folows:
+            //      - Unpadded length in bytes = `mload(receiverData) + 32`
+            //      - Add 31 to convert rounding down to rounding up.
+            //        Combined with the previous and this is `63`.
+            //      - Round down to nearest multiple of 32 by clearing
+            //        bits 0x1F. This is done with `and` and a mask.
+
+            /////// Setup Header Area ///////
+            // This area holds the 4-byte `transferFromSelector`.
+            // Any trailing data in transferFromSelector will be
+            // overwritten in the next `mstore` call.
+            mstore(cdStart, 0xb88d4fde00000000000000000000000000000000000000000000000000000000)
+            
+            /////// Setup Params Area ///////
+            // Each parameter is padded to 32-bytes.
+            // The entire Params Area is 128 bytes.
+            // Notes:
+            //   1. A 20-byte mask is applied to addresses
+            //      to zero-out the unused bytes.
+            //   2. The offset to `receiverData` is the length
+            //      of the Params Area (128 bytes).
+            
+            let length := calldataload(add(offset, 136))
+            let token := calldataload(add(offset, 40))
+            
+            // Round length up to multiple of 32
+            length := and(add(length, 31), 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE0)
+            
+            // Copy `from` and `to`
+            calldatacopy(add(cdStart, 4), 36, 64)
+            
+            // TokenId
+            mstore(add(cdStart, 68), calldataload(add(offset, 72)))
+            
+            // Offset to receiverData
+            mstore(add(cdStart, 100), 128)
+            
+            // receiverData (including length)
+            calldatacopy(add(cdStart, 132), add(offset, 136), add(length, 32))
+            
+            /////// Call `token.safeTransferFrom` using the calldata ///////
+            let success := call(
+                gas,                    // forward all gas
+                token,                  // call address of token contract
+                0,                      // don't send any ETH
+                cdStart,                // pointer to start of input
+                add(length, 164),       // length of input
+                0,                      // write output to null
+                0                       // output size is 0 bytes
+            )
+            if success {
+                return(0, 0)
+            }
+            
+            // Revert with `Error("TRANSFER_FAILED")`
+            mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000)
+            mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000)
+            mstore(64, 0x0000000f5452414e534645525f4641494c454400000000000000000000000000)
+            mstore(96, 0)
+            revert(0, 100)
+        }
+    }
 
     /// @dev Gets the proxy id associated with the proxy address.
     /// @return Proxy id.
     function getProxyId()
         external
         view
-        returns (uint8)
+        returns (bytes4)
     {
         return PROXY_ID;
     }
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol
deleted file mode 100644
index 9032658e7..000000000
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAssetProxy.sol
+++ /dev/null
@@ -1,75 +0,0 @@
-/*
-
-  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 "./mixins/MAuthorizable.sol";
-import "./mixins/MAssetProxy.sol";
-
-contract MixinAssetProxy is
-    MAuthorizable,
-    MAssetProxy
-{
-
-    /// @dev Transfers assets. Either succeeds or throws.
-    /// @param assetData Encoded byte array.
-    /// @param from Address to transfer asset from.
-    /// @param to Address to transfer asset to.
-    /// @param amount Amount of asset to transfer.
-    function transferFrom(
-        bytes assetData,
-        address from,
-        address to,
-        uint256 amount
-    )
-        external
-        onlyAuthorized
-    {
-        transferFromInternal(
-            assetData,
-            from,
-            to,
-            amount
-        );
-    }
-
-    /// @dev Makes multiple transfers of assets. Either succeeds or throws.
-    /// @param assetData Array of byte arrays encoded for the respective asset proxy.
-    /// @param from Array of addresses to transfer assets from.
-    /// @param to Array of addresses to transfer assets to.
-    /// @param amounts Array of amounts of assets to transfer.
-    function batchTransferFrom(
-        bytes[] memory assetData,
-        address[] memory from,
-        address[] memory to,
-        uint256[] memory amounts
-    )
-        public
-        onlyAuthorized
-    {
-        for (uint256 i = 0; i < assetData.length; i++) {
-            transferFromInternal(
-                assetData[i],
-                from[i],
-                to[i],
-                amounts[i]
-            );
-        }
-    }
-}
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAuthorizable.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAuthorizable.sol
index 37c12f861..3b9584a44 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAuthorizable.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinAuthorizable.sol
@@ -19,12 +19,10 @@
 pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
-import "./libs/LibAssetProxyErrors.sol";
 import "../../utils/Ownable/Ownable.sol";
 import "./mixins/MAuthorizable.sol";
 
 contract MixinAuthorizable is
-    LibAssetProxyErrors,
     Ownable,
     MAuthorizable
 {
@@ -33,7 +31,7 @@ contract MixinAuthorizable is
     modifier onlyAuthorized {
         require(
             authorized[msg.sender],
-            SENDER_NOT_AUTHORIZED
+            "SENDER_NOT_AUTHORIZED"
         );
         _;
     }
@@ -49,7 +47,7 @@ contract MixinAuthorizable is
     {
         require(
             !authorized[target],
-            TARGET_ALREADY_AUTHORIZED
+            "TARGET_ALREADY_AUTHORIZED"
         );
 
         authorized[target] = true;
@@ -65,7 +63,7 @@ contract MixinAuthorizable is
     {
         require(
             authorized[target],
-            TARGET_NOT_AUTHORIZED
+            "TARGET_NOT_AUTHORIZED"
         );
 
         delete authorized[target];
@@ -91,15 +89,15 @@ contract MixinAuthorizable is
     {
         require(
             authorized[target],
-            TARGET_NOT_AUTHORIZED
+            "TARGET_NOT_AUTHORIZED"
         );
         require(
             index < authorities.length,
-            INDEX_OUT_OF_BOUNDS
+            "INDEX_OUT_OF_BOUNDS"
         );
         require(
             authorities[index] == target,
-            AUTHORIZED_ADDRESS_MISMATCH
+            "AUTHORIZED_ADDRESS_MISMATCH"
         );
 
         delete authorized[target];
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinERC20Transfer.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinERC20Transfer.sol
deleted file mode 100644
index 0e7f3fc89..000000000
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinERC20Transfer.sol
+++ /dev/null
@@ -1,82 +0,0 @@
-/*
-
-  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/IERC20Token.sol";
-import "./libs/LibTransferErrors.sol";
-
-contract MixinERC20Transfer is
-    LibTransferErrors
-{
-    using LibBytes for bytes;
-
-    /// @dev Internal version of `transferFrom`.
-    /// @param assetData Encoded byte array.
-    /// @param from Address to transfer asset from.
-    /// @param to Address to transfer asset to.
-    /// @param amount Amount of asset to transfer.
-    function transferFromInternal(
-        bytes memory assetData,
-        address from,
-        address to,
-        uint256 amount
-    )
-        internal
-    {
-        // Decode asset data.
-        address token = assetData.readAddress(0);
-
-        // Transfer tokens.
-        // We do a raw call so we can check the success separate
-        // from the return data.
-        bool success = token.call(abi.encodeWithSelector(
-            IERC20Token(token).transferFrom.selector,
-            from,
-            to,
-            amount
-        ));
-        require(
-            success,
-            TRANSFER_FAILED
-        );
-        
-        // Check return data.
-        // If there is no return data, we assume the token incorrectly
-        // does not return a bool. In this case we expect it to revert
-        // on failure, which was handled above.
-        // If the token does return data, we require that it is a single
-        // value that evaluates to true.
-        assembly {
-            if returndatasize {
-                success := 0
-                if eq(returndatasize, 32) {
-                    // First 64 bytes of memory are reserved scratch space
-                    returndatacopy(0, 0, 32)
-                    success := mload(0)
-                }
-            }
-        }
-        require(
-            success,
-            TRANSFER_FAILED
-        );
-    }
-}
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinERC721Transfer.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinERC721Transfer.sol
deleted file mode 100644
index 944068bbb..000000000
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/MixinERC721Transfer.sol
+++ /dev/null
@@ -1,94 +0,0 @@
-/*
-
-  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/ERC721Token/ERC721Token.sol";
-import "./libs/LibTransferErrors.sol";
-
-contract MixinERC721Transfer is
-    LibTransferErrors
-{
-    using LibBytes for bytes;
-    
-    /// @dev Internal version of `transferFrom`.
-    /// @param assetData Encoded byte array.
-    /// @param from Address to transfer asset from.
-    /// @param to Address to transfer asset to.
-    /// @param amount Amount of asset to transfer.
-    function transferFromInternal(
-        bytes memory assetData,
-        address from,
-        address to,
-        uint256 amount
-    )
-        internal
-    {
-        // There exists only 1 of each token.
-        require(
-            amount == 1,
-            INVALID_AMOUNT
-        );
-    
-        // Decode asset data.
-        (
-            address token,
-            uint256 tokenId,
-            bytes memory receiverData
-        ) = decodeERC721AssetData(assetData);
-
-        ERC721Token(token).safeTransferFrom(
-            from,
-            to,
-            tokenId,
-            receiverData
-        );
-    }
-
-    /// @dev Decodes ERC721 Asset data.
-    /// @param assetData Encoded byte array.
-    /// @return proxyId Intended ERC721 proxy id.
-    /// @return token ERC721 token address.
-    /// @return tokenId ERC721 token id.
-    /// @return receiverData Additional data with no specific format, which
-    ///                      is passed to the receiving contract's onERC721Received.
-    function decodeERC721AssetData(bytes memory assetData)
-        internal
-        pure
-        returns (
-            address token,
-            uint256 tokenId,
-            bytes memory receiverData
-        )
-    {
-        // Decode asset data.
-        token = assetData.readAddress(0);
-        tokenId = assetData.readUint256(20);
-        if (assetData.length > 52) {
-            receiverData = assetData.readBytesWithLength(52);
-        }
-
-        return (
-            token,
-            tokenId,
-            receiverData
-        );
-    }
-}
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/libs/LibTransferErrors.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetData.sol
index ba784ab22..8c78ee8c4 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/libs/LibTransferErrors.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetData.sol
@@ -16,10 +16,21 @@
 
 */
 
-pragma solidity ^0.4.24;
+pragma solidity ^0.4.23;
 
-contract LibTransferErrors {
-    /// Transfer errors ///
-    string constant INVALID_AMOUNT = "INVALID_AMOUNT";                            // Transfer amount must equal 1.
-    string constant TRANSFER_FAILED = "TRANSFER_FAILED";                          // Transfer failed.
+// @dev Interface of the asset proxy's assetData.
+// The asset proxies take an ABI encoded `bytes assetData` as argument.
+// This argument is ABI encoded as one of the methods of this interface.
+interface IAssetData {
+    
+    function ERC20Token(
+        address tokenContract)
+        external pure;
+    
+    function ERC721Token(
+        address tokenContract,
+        uint256 tokenId,
+        bytes receiverData)
+        external pure;
+    
 }
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetProxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetProxy.sol
index 22f43b12f..ae8e195da 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetProxy.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/interfaces/IAssetProxy.sol
@@ -38,24 +38,10 @@ contract IAssetProxy is
     )
         external;
     
-    /// @dev Makes multiple transfers of assets. Either succeeds or throws.
-    /// @param assetData Array of byte arrays encoded for the respective asset proxy.
-    /// @param from Array of addresses to transfer assets from.
-    /// @param to Array of addresses to transfer assets to.
-    /// @param amounts Array of amounts of assets to transfer.
-    function batchTransferFrom(
-        bytes[] memory assetData,
-        address[] memory from,
-        address[] memory to,
-        uint256[] memory amounts
-    )
-        public;
-
     /// @dev Gets the proxy id associated with the proxy address.
     /// @return Proxy id.
     function getProxyId()
         external
         view
-        returns (uint8);
+        returns (bytes4);
 }
-
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/libs/LibAssetProxyErrors.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/libs/LibAssetProxyErrors.sol
index dca4f400f..338cb12e2 100644
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/libs/LibAssetProxyErrors.sol
+++ b/packages/contracts/src/contracts/current/protocol/AssetProxy/libs/LibAssetProxyErrors.sol
@@ -18,11 +18,19 @@
 
 pragma solidity ^0.4.24;
 
+/// @dev This contract documents the revert reasons used in the AssetProxy contracts.
+/// This contract is intended to serve as a reference, but is not actually used for efficiency reasons.
 contract LibAssetProxyErrors {
+
     /// Authorizable errors ///
-    string constant SENDER_NOT_AUTHORIZED = "SENDER_NOT_AUTHORIZED";              // Sender not authorized to call this method.
-    string constant TARGET_NOT_AUTHORIZED = "TARGET_NOT_AUTHORIZED";              // Target address not authorized to call this method.
-    string constant TARGET_ALREADY_AUTHORIZED = "TARGET_ALREADY_AUTHORIZED";      // Target address must not already be authorized.
-    string constant INDEX_OUT_OF_BOUNDS = "INDEX_OUT_OF_BOUNDS";                  // Specified array index is out of bounds.
-    string constant AUTHORIZED_ADDRESS_MISMATCH = "AUTHORIZED_ADDRESS_MISMATCH";  // Address at index does not match given target address.
+    string constant SENDER_NOT_AUTHORIZED = "SENDER_NOT_AUTHORIZED";                        // Sender not authorized to call this method.
+    string constant TARGET_NOT_AUTHORIZED = "TARGET_NOT_AUTHORIZED";                        // Target address not authorized to call this method.
+    string constant TARGET_ALREADY_AUTHORIZED = "TARGET_ALREADY_AUTHORIZED";                // Target address must not already be authorized.
+    string constant INDEX_OUT_OF_BOUNDS = "INDEX_OUT_OF_BOUNDS";                            // Specified array index is out of bounds.
+    string constant AUTHORIZED_ADDRESS_MISMATCH = "AUTHORIZED_ADDRESS_MISMATCH";            // Address at index does not match given target address.
+
+    /// Transfer errors ///
+    string constant INVALID_AMOUNT = "INVALID_AMOUNT";                                      // Transfer amount must equal 1.
+    string constant TRANSFER_FAILED = "TRANSFER_FAILED";                                    // Transfer failed.
+    string constant LENGTH_GREATER_THAN_131_REQUIRED = "LENGTH_GREATER_THAN_131_REQUIRED";  // Byte array must have a length greater than 0.
 }
diff --git a/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAssetProxy.sol b/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAssetProxy.sol
deleted file mode 100644
index a52cb56f9..000000000
--- a/packages/contracts/src/contracts/current/protocol/AssetProxy/mixins/MAssetProxy.sol
+++ /dev/null
@@ -1,40 +0,0 @@
-/*
-
-  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 "../interfaces/IAssetProxy.sol";
-
-contract MAssetProxy is
-    IAssetProxy
-{
-
-    /// @dev Internal version of `transferFrom`.
-    /// @param assetData Encoded byte array.
-    /// @param from Address to transfer asset from.
-    /// @param to Address to transfer asset to.
-    /// @param amount Amount of asset to transfer.
-    function transferFromInternal(
-        bytes memory assetData,
-        address from,
-        address to,
-        uint256 amount
-    )
-        internal;
-}
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
index b8d6c0722..f7086f543 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol
@@ -19,17 +19,18 @@
 pragma solidity ^0.4.24;
 
 import "../../utils/Ownable/Ownable.sol";
-import "./libs/LibExchangeErrors.sol";
+import "../../utils/LibBytes/LibBytes.sol";
 import "./mixins/MAssetProxyDispatcher.sol";
 import "../AssetProxy/interfaces/IAssetProxy.sol";
 
 contract MixinAssetProxyDispatcher is
     Ownable,
-    LibExchangeErrors,
     MAssetProxyDispatcher
 {
+    using LibBytes for bytes;
+    
     // Mapping from Asset Proxy Id's to their respective Asset Proxy
-    mapping (uint8 => IAssetProxy) public assetProxies;
+    mapping (bytes4 => IAssetProxy) public assetProxies;
 
     /// @dev Registers an asset proxy to an asset proxy id.
     ///      An id can only be assigned to a single proxy at a given time.
@@ -37,7 +38,7 @@ contract MixinAssetProxyDispatcher is
     /// @param newAssetProxy Address of new asset proxy to register, or 0x0 to unset assetProxyId.
     /// @param oldAssetProxy Existing asset proxy to overwrite, or 0x0 if assetProxyId is currently unused.
     function registerAssetProxy(
-        uint8 assetProxyId,
+        bytes4 assetProxyId,
         address newAssetProxy,
         address oldAssetProxy
     )
@@ -48,17 +49,17 @@ contract MixinAssetProxyDispatcher is
         address currentAssetProxy = assetProxies[assetProxyId];
         require(
             oldAssetProxy == currentAssetProxy,
-            ASSET_PROXY_MISMATCH
+            "ASSET_PROXY_MISMATCH"
         );
 
         IAssetProxy assetProxy = IAssetProxy(newAssetProxy);
 
         // Ensure that the id of newAssetProxy matches the passed in assetProxyId, unless it is being reset to 0.
         if (newAssetProxy != address(0)) {
-            uint8 newAssetProxyId = assetProxy.getProxyId();
+            bytes4 newAssetProxyId = assetProxy.getProxyId();
             require(
                 newAssetProxyId == assetProxyId,
-                ASSET_PROXY_ID_MISMATCH
+                "ASSET_PROXY_ID_MISMATCH"
             );
         }
 
@@ -74,7 +75,7 @@ contract MixinAssetProxyDispatcher is
     /// @dev Gets an asset proxy.
     /// @param assetProxyId Id of the asset proxy.
     /// @return The asset proxy registered to assetProxyId. Returns 0x0 if no proxy is registered.
-    function getAssetProxy(uint8 assetProxyId)
+    function getAssetProxy(bytes4 assetProxyId)
         external
         view
         returns (address)
@@ -83,14 +84,12 @@ contract MixinAssetProxyDispatcher is
     }
 
     /// @dev Forwards arguments to assetProxy and calls `transferFrom`. Either succeeds or throws.
-    /// @param assetData Byte array encoded for the respective asset proxy.
-    /// @param assetProxyId Id of assetProxy to dispach to.
+    /// @param assetData Byte array encoded for the asset.
     /// @param from Address to transfer token from.
     /// @param to Address to transfer token to.
     /// @param amount Amount of token to transfer.
     function dispatchTransferFrom(
         bytes memory assetData,
-        uint8 assetProxyId,
         address from,
         address to,
         uint256 amount
@@ -99,20 +98,94 @@ contract MixinAssetProxyDispatcher is
     {
         // Do nothing if no amount should be transferred.
         if (amount > 0) {
+            // Ensure assetData length is valid
+            require(
+                assetData.length > 3,
+                "LENGTH_GREATER_THAN_3_REQUIRED"
+            );
+            
             // Lookup assetProxy
+            bytes4 assetProxyId;
+            assembly {
+                assetProxyId := and(mload(
+                    add(assetData, 32)),
+                    0xFFFFFFFF00000000000000000000000000000000000000000000000000000000
+                )
+            }
             IAssetProxy assetProxy = assetProxies[assetProxyId];
+
             // Ensure that assetProxy exists
             require(
                 assetProxy != address(0),
-                ASSET_PROXY_DOES_NOT_EXIST
-            );
-            // transferFrom will either succeed or throw.
-            assetProxy.transferFrom(
-                assetData,
-                from,
-                to,
-                amount
+                "ASSET_PROXY_DOES_NOT_EXIST"
             );
+            
+            // We construct calldata for the `assetProxy.transferFrom` ABI.
+            // The layout of this calldata is in the table below.
+            // 
+            // | Area     | Offset | Length  | Contents                                    |
+            // | -------- |--------|---------|-------------------------------------------- |
+            // | Header   | 0      | 4       | function selector                           |
+            // | Params   |        | 4 * 32  | function parameters:                        |
+            // |          | 4      |         |   1. offset to assetData (*)                |
+            // |          | 36     |         |   2. from                                   |
+            // |          | 68     |         |   3. to                                     |
+            // |          | 100    |         |   4. amount                                 |
+            // | Data     |        |         | assetData:                                  |
+            // |          | 132    | 32      | assetData Length                            |
+            // |          | 164    | **      | assetData Contents                          |
+
+            bool success;
+            assembly {
+                /////// Setup State ///////
+                // `cdStart` is the start of the calldata for `assetProxy.transferFrom` (equal to free memory ptr).
+                let cdStart := mload(64)
+                // `dataAreaLength` is the total number of words needed to store `assetData`
+                //  As-per the ABI spec, this value is padded up to the nearest multiple of 32,
+                //  and includes 32-bytes for length.
+                let dataAreaLength := and(add(mload(assetData), 63), 0xFFFFFFFFFFFE0)
+                // `cdEnd` is the end of the calldata for `assetProxy.transferFrom`.
+                let cdEnd := add(cdStart, add(132, dataAreaLength))
+
+                
+                /////// Setup Header Area ///////
+                // This area holds the 4-byte `transferFromSelector`.
+                // bytes4(keccak256("transferFrom(bytes,address,address,uint256)")) = 0xa85e59e4
+                mstore(cdStart, 0xa85e59e400000000000000000000000000000000000000000000000000000000)
+                
+                /////// Setup Params Area ///////
+                // Each parameter is padded to 32-bytes. The entire Params Area is 128 bytes.
+                // Notes:
+                //   1. The offset to `assetData` is the length of the Params Area (128 bytes).
+                //   2. A 20-byte mask is applied to addresses to zero-out the unused bytes.
+                mstore(add(cdStart, 4), 128)
+                mstore(add(cdStart, 36), and(from, 0xffffffffffffffffffffffffffffffffffffffff))
+                mstore(add(cdStart, 68), and(to, 0xffffffffffffffffffffffffffffffffffffffff))
+                mstore(add(cdStart, 100), amount)
+                
+                /////// Setup Data Area ///////
+                // This area holds `assetData`.
+                let dataArea := add(cdStart, 132)
+                for {} lt(dataArea, cdEnd) {} {
+                    mstore(dataArea, mload(assetData))
+                    dataArea := add(dataArea, 32)
+                    assetData := add(assetData, 32)
+                }
+
+                /////// Call `assetProxy.transferFrom` using the constructed calldata ///////
+                success := call(
+                    gas,                    // forward all gas
+                    assetProxy,             // call address of asset proxy
+                    0,                      // don't send any ETH
+                    cdStart,                // pointer to start of input
+                    sub(cdEnd, cdStart),    // length of input  
+                    cdStart,                // write output over input
+                    512                     // reserve 512 bytes for output
+                )
+                if eq(success, 0) {
+                    revert(cdStart, returndatasize())
+                }
+            }
         }
     }
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinExchangeCore.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinExchangeCore.sol
index b207b3e57..c0ed023ac 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinExchangeCore.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinExchangeCore.sol
@@ -20,11 +20,9 @@ pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "./libs/LibConstants.sol";
-import "../../utils/LibBytes/LibBytes.sol";
 import "./libs/LibFillResults.sol";
 import "./libs/LibOrder.sol";
 import "./libs/LibMath.sol";
-import "./libs/LibExchangeErrors.sol";
 import "./mixins/MExchangeCore.sol";
 import "./mixins/MSignatureValidator.sol";
 import "./mixins/MTransactions.sol";
@@ -35,14 +33,11 @@ contract MixinExchangeCore is
     LibMath,
     LibOrder,
     LibFillResults,
-    LibExchangeErrors,
     MAssetProxyDispatcher,
     MExchangeCore,
     MSignatureValidator,
     MTransactions
 {
-    using LibBytes for bytes;
-    
     // Mapping of orderHash => amount of takerAsset already bought by maker
     mapping (bytes32 => uint256) public filled;
 
@@ -73,7 +68,7 @@ contract MixinExchangeCore is
         // Ensure orderEpoch is monotonically increasing
         require(
             newOrderEpoch > oldOrderEpoch, 
-            INVALID_NEW_ORDER_EPOCH
+            "INVALID_NEW_ORDER_EPOCH"
         );
 
         // Update orderEpoch
@@ -285,20 +280,20 @@ contract MixinExchangeCore is
         // An order can only be filled if its status is FILLABLE.
         require(
             orderInfo.orderStatus == uint8(OrderStatus.FILLABLE),
-            ORDER_UNFILLABLE
+            "ORDER_UNFILLABLE"
         );
 
         // Revert if fill amount is invalid
         require(
             takerAssetFillAmount != 0,
-            INVALID_TAKER_AMOUNT
+            "INVALID_TAKER_AMOUNT"
         );
 
         // Validate sender is allowed to fill this order
         if (order.senderAddress != address(0)) {
             require(
                 order.senderAddress == msg.sender,
-                INVALID_SENDER
+                "INVALID_SENDER"
             );
         }
 
@@ -306,7 +301,7 @@ contract MixinExchangeCore is
         if (order.takerAddress != address(0)) {
             require(
                 order.takerAddress == takerAddress,
-                INVALID_TAKER
+                "INVALID_TAKER"
             );
         }
 
@@ -318,7 +313,7 @@ contract MixinExchangeCore is
                     order.makerAddress,
                     signature
                 ),
-                INVALID_ORDER_SIGNATURE
+                "INVALID_ORDER_SIGNATURE"
             );
         }
 
@@ -329,7 +324,7 @@ contract MixinExchangeCore is
                 order.takerAssetAmount,
                 order.makerAssetAmount
             ),
-            ROUNDING_ERROR
+            "ROUNDING_ERROR"
         );
     }
 
@@ -347,14 +342,14 @@ contract MixinExchangeCore is
         // An order can only be cancelled if its status is FILLABLE.
         require(
             orderInfo.orderStatus == uint8(OrderStatus.FILLABLE),
-            ORDER_UNFILLABLE
+            "ORDER_UNFILLABLE"
         );
 
         // Validate sender is allowed to cancel this order
         if (order.senderAddress != address(0)) {
             require(
                 order.senderAddress == msg.sender,
-                INVALID_SENDER
+                "INVALID_SENDER"
             );
         }
 
@@ -362,7 +357,7 @@ contract MixinExchangeCore is
         address makerAddress = getCurrentContextAddress();
         require(
             order.makerAddress == makerAddress,
-            INVALID_MAKER
+            "INVALID_MAKER"
         );
     }
 
@@ -412,33 +407,27 @@ contract MixinExchangeCore is
     )
         private
     {
-        uint8 makerAssetProxyId = uint8(order.makerAssetData.popLastByte());
-        uint8 takerAssetProxyId = uint8(order.takerAssetData.popLastByte());
         bytes memory zrxAssetData = ZRX_ASSET_DATA;
         dispatchTransferFrom(
             order.makerAssetData,
-            makerAssetProxyId,
             order.makerAddress,
             takerAddress,
             fillResults.makerAssetFilledAmount
         );
         dispatchTransferFrom(
             order.takerAssetData,
-            takerAssetProxyId,
             takerAddress,
             order.makerAddress,
             fillResults.takerAssetFilledAmount
         );
         dispatchTransferFrom(
             zrxAssetData,
-            ZRX_PROXY_ID,
             order.makerAddress,
             order.feeRecipientAddress,
             fillResults.makerFeePaid
         );
         dispatchTransferFrom(
             zrxAssetData,
-            ZRX_PROXY_ID,
             takerAddress,
             order.feeRecipientAddress,
             fillResults.takerFeePaid
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinMatchOrders.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinMatchOrders.sol
index e36fcc2c5..1a43eec79 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinMatchOrders.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinMatchOrders.sol
@@ -15,11 +15,9 @@ pragma solidity ^0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "./libs/LibConstants.sol";
-import "../../utils/LibBytes/LibBytes.sol";
 import "./libs/LibMath.sol";
 import "./libs/LibOrder.sol";
 import "./libs/LibFillResults.sol";
-import "./libs/LibExchangeErrors.sol";
 import "./mixins/MExchangeCore.sol";
 import "./mixins/MMatchOrders.sol";
 import "./mixins/MTransactions.sol";
@@ -28,14 +26,11 @@ import "./mixins/MAssetProxyDispatcher.sol";
 contract MixinMatchOrders is
     LibConstants,
     LibMath,
-    LibExchangeErrors,
     MAssetProxyDispatcher,
     MExchangeCore,
     MMatchOrders,
     MTransactions
 {
-    using LibBytes for bytes;
-
     /// @dev Match two complementary orders that have a profitable spread.
     ///      Each order is filled at their respective price point. However, the calculations are
     ///      carried out as though the orders are both being filled at the right order's price point.
@@ -144,7 +139,7 @@ contract MixinMatchOrders is
         require(
             safeMul(leftOrder.makerAssetAmount, rightOrder.makerAssetAmount) >=
             safeMul(leftOrder.takerAssetAmount, rightOrder.takerAssetAmount),
-            NEGATIVE_SPREAD_REQUIRED
+            "NEGATIVE_SPREAD_REQUIRED"
         );
     }
 
@@ -242,27 +237,22 @@ contract MixinMatchOrders is
     )
         private
     {
-        uint8 leftMakerAssetProxyId = uint8(leftOrder.makerAssetData.popLastByte());
-        uint8 rightMakerAssetProxyId = uint8(rightOrder.makerAssetData.popLastByte());
         bytes memory zrxAssetData = ZRX_ASSET_DATA;
         // Order makers and taker
         dispatchTransferFrom(
             leftOrder.makerAssetData,
-            leftMakerAssetProxyId,
             leftOrder.makerAddress,
             rightOrder.makerAddress,
             matchedFillResults.right.takerAssetFilledAmount
         );
         dispatchTransferFrom(
             rightOrder.makerAssetData,
-            rightMakerAssetProxyId,
             rightOrder.makerAddress,
             leftOrder.makerAddress,
             matchedFillResults.left.takerAssetFilledAmount
         );
         dispatchTransferFrom(
             leftOrder.makerAssetData,
-            leftMakerAssetProxyId,
             leftOrder.makerAddress,
             takerAddress,
             matchedFillResults.leftMakerAssetSpreadAmount
@@ -271,14 +261,12 @@ contract MixinMatchOrders is
         // Maker fees
         dispatchTransferFrom(
             zrxAssetData,
-            ZRX_PROXY_ID,
             leftOrder.makerAddress,
             leftOrder.feeRecipientAddress,
             matchedFillResults.left.makerFeePaid
         );
         dispatchTransferFrom(
             zrxAssetData,
-            ZRX_PROXY_ID,
             rightOrder.makerAddress,
             rightOrder.feeRecipientAddress,
             matchedFillResults.right.makerFeePaid
@@ -288,7 +276,6 @@ contract MixinMatchOrders is
         if (leftOrder.feeRecipientAddress == rightOrder.feeRecipientAddress) {
             dispatchTransferFrom(
                 zrxAssetData,
-                ZRX_PROXY_ID,
                 takerAddress,
                 leftOrder.feeRecipientAddress,
                 safeAdd(
@@ -299,14 +286,12 @@ contract MixinMatchOrders is
         } else {
             dispatchTransferFrom(
                 zrxAssetData,
-                ZRX_PROXY_ID,
                 takerAddress,
                 leftOrder.feeRecipientAddress,
                 matchedFillResults.left.takerFeePaid
             );
             dispatchTransferFrom(
                 zrxAssetData,
-                ZRX_PROXY_ID,
                 takerAddress,
                 rightOrder.feeRecipientAddress,
                 matchedFillResults.right.takerFeePaid
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
index cbb55bfce..29172057a 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
@@ -19,23 +19,17 @@
 pragma solidity ^0.4.24;
 
 import "../../utils/LibBytes/LibBytes.sol";
-import "./libs/LibExchangeErrors.sol";
 import "./mixins/MSignatureValidator.sol";
 import "./mixins/MTransactions.sol";
 import "./interfaces/IWallet.sol";
 import "./interfaces/IValidator.sol";
 
 contract MixinSignatureValidator is
-    LibExchangeErrors,
     MSignatureValidator,
     MTransactions
 {
     using LibBytes for bytes;
     
-    // Personal message headers
-    string constant ETH_PERSONAL_MESSAGE = "\x19Ethereum Signed Message:\n32";
-    string constant TREZOR_PERSONAL_MESSAGE = "\x19Ethereum Signed Message:\n\x20";
-
     // Mapping of hash => signer => signed
     mapping (bytes32 => mapping (address => bool)) public preSigned;
 
@@ -59,7 +53,7 @@ contract MixinSignatureValidator is
                 signerAddress,
                 signature
             ),
-            INVALID_SIGNATURE
+            "INVALID_SIGNATURE"
         );
         preSigned[hash][signerAddress] = true;
     }
@@ -99,14 +93,14 @@ contract MixinSignatureValidator is
         // TODO: Domain separation: make hash depend on role. (Taker sig should not be valid as maker sig, etc.)
         require(
             signature.length > 0,
-            LENGTH_GREATER_THAN_0_REQUIRED
+            "LENGTH_GREATER_THAN_0_REQUIRED"
         );
 
         // Ensure signature is supported
         uint8 signatureTypeRaw = uint8(signature.popLastByte());
         require(
             signatureTypeRaw < uint8(SignatureType.NSignatureTypes),
-            SIGNATURE_UNSUPPORTED
+            "SIGNATURE_UNSUPPORTED"
         );
 
         // Pop last byte off of signature byte array.
@@ -124,7 +118,7 @@ contract MixinSignatureValidator is
         // it an explicit option. This aids testing and analysis. It is
         // also the initialization value for the enum type.
         if (signatureType == SignatureType.Illegal) {
-            revert(SIGNATURE_ILLEGAL);
+            revert("SIGNATURE_ILLEGAL");
 
         // Always invalid signature.
         // Like Illegal, this is always implicitly available and therefore
@@ -133,7 +127,7 @@ contract MixinSignatureValidator is
         } else if (signatureType == SignatureType.Invalid) {
             require(
                 signature.length == 0,
-                LENGTH_0_REQUIRED
+                "LENGTH_0_REQUIRED"
             );
             isValid = false;
             return isValid;
@@ -142,7 +136,7 @@ contract MixinSignatureValidator is
         } else if (signatureType == SignatureType.EIP712) {
             require(
                 signature.length == 65,
-                LENGTH_65_REQUIRED
+                "LENGTH_65_REQUIRED"
             );
             v = uint8(signature[0]);
             r = signature.readBytes32(1);
@@ -155,13 +149,16 @@ contract MixinSignatureValidator is
         } else if (signatureType == SignatureType.EthSign) {
             require(
                 signature.length == 65,
-                LENGTH_65_REQUIRED
+                "LENGTH_65_REQUIRED"
             );
             v = uint8(signature[0]);
             r = signature.readBytes32(1);
             s = signature.readBytes32(33);
             recovered = ecrecover(
-                keccak256(abi.encodePacked(ETH_PERSONAL_MESSAGE, hash)),
+                keccak256(abi.encodePacked(
+                    "\x19Ethereum Signed Message:\n32",
+                    hash
+                )),
                 v,
                 r,
                 s
@@ -180,7 +177,7 @@ contract MixinSignatureValidator is
         } else if (signatureType == SignatureType.Caller) {
             require(
                 signature.length == 0,
-                LENGTH_0_REQUIRED
+                "LENGTH_0_REQUIRED"
             );
             isValid = signerAddress == msg.sender;
             return isValid;
@@ -230,13 +227,16 @@ contract MixinSignatureValidator is
         } else if (signatureType == SignatureType.Trezor) {
             require(
                 signature.length == 65,
-                LENGTH_65_REQUIRED
+                "LENGTH_65_REQUIRED"
             );
             v = uint8(signature[0]);
             r = signature.readBytes32(1);
             s = signature.readBytes32(33);
             recovered = ecrecover(
-                keccak256(abi.encodePacked(TREZOR_PERSONAL_MESSAGE, hash)),
+                keccak256(abi.encodePacked(
+                    "\x19Ethereum Signed Message:\n\x20",
+                    hash
+                )),
                 v,
                 r,
                 s
@@ -250,6 +250,6 @@ contract MixinSignatureValidator is
         // that we currently support. In this case returning false
         // may lead the caller to incorrectly believe that the
         // signature was invalid.)
-        revert(SIGNATURE_UNSUPPORTED);
+        revert("SIGNATURE_UNSUPPORTED");
     }
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinTransactions.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinTransactions.sol
index 20a4a12df..e0f450d0a 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinTransactions.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinTransactions.sol
@@ -20,12 +20,10 @@ pragma solidity ^0.4.24;
 import "./libs/LibExchangeErrors.sol";
 import "./mixins/MSignatureValidator.sol";
 import "./mixins/MTransactions.sol";
-import "./libs/LibExchangeErrors.sol";
 import "./libs/LibEIP712.sol";
 
 contract MixinTransactions is
     LibEIP712,
-    LibExchangeErrors,
     MSignatureValidator,
     MTransactions
 {
@@ -90,7 +88,7 @@ contract MixinTransactions is
         // Prevent reentrancy
         require(
             currentContextAddress == address(0),
-            REENTRANCY_ILLEGAL
+            "REENTRANCY_ILLEGAL"
         );
 
         bytes32 transactionHash = hashEIP712Message(hashZeroExTransaction(
@@ -102,7 +100,7 @@ contract MixinTransactions is
         // Validate transaction has not been executed
         require(
             !transactions[transactionHash],
-            INVALID_TX_HASH
+            "INVALID_TX_HASH"
         );
 
         // Transaction always valid if signer is sender of transaction
@@ -114,7 +112,7 @@ contract MixinTransactions is
                     signerAddress,
                     signature
                 ),
-                INVALID_TX_SIGNATURE
+                "INVALID_TX_SIGNATURE"
             );
 
             // Set the current transaction signer
@@ -125,7 +123,7 @@ contract MixinTransactions is
         transactions[transactionHash] = true;
         require(
             address(this).delegatecall(data),
-            FAILED_EXECUTION
+            "FAILED_EXECUTION"
         );
 
         // Reset current transaction signer
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol b/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol
index 724f95518..00668ca43 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/MixinWrapperFunctions.sol
@@ -22,13 +22,11 @@ pragma experimental ABIEncoderV2;
 import "./libs/LibMath.sol";
 import "./libs/LibOrder.sol";
 import "./libs/LibFillResults.sol";
-import "./libs/LibExchangeErrors.sol";
 import "./mixins/MExchangeCore.sol";
 
 contract MixinWrapperFunctions is
     LibMath,
     LibFillResults,
-    LibExchangeErrors,
     MExchangeCore
 {
     /// @dev Fills the input order. Reverts if exact takerAssetFillAmount not filled.
@@ -50,7 +48,7 @@ contract MixinWrapperFunctions is
         );
         require(
             fillResults.takerAssetFilledAmount == takerAssetFillAmount,
-            COMPLETE_FILL_FAILED
+            "COMPLETE_FILL_FAILED"
         );
         return fillResults;
     }
@@ -366,14 +364,6 @@ contract MixinWrapperFunctions is
                 signatures[i]
             );
 
-            // HACK: the proxyId is "popped" from the byte array before a fill is settled
-            // by subtracting from the length of the array. Since the popped byte is 
-            // still in memory, we can "unpop" it by incrementing the length of the byte array.
-            assembly {
-                let len := mload(takerAssetData)
-                mstore(takerAssetData, add(len, 1))
-            }
-
             // Update amounts filled and fees paid by maker and taker
             addFillResults(totalFillResults, singleFillResults);
 
@@ -467,14 +457,6 @@ contract MixinWrapperFunctions is
                 signatures[i]
             );
 
-            // HACK: the proxyId is "popped" from the byte array before a fill is settled
-            // by subtracting from the length of the array. Since the popped byte is 
-            // still in memory, we can "unpop" it by incrementing the length of the byte array.
-            assembly {
-                let len := mload(makerAssetData)
-                mstore(makerAssetData, add(len, 1))
-            }
-
             // Update amounts filled and fees paid by maker and taker
             addFillResults(totalFillResults, singleFillResults);
 
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IAssetProxyDispatcher.sol
index 2c331dc34..fa55dff00 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/interfaces/IAssetProxyDispatcher.sol
@@ -26,7 +26,7 @@ contract IAssetProxyDispatcher {
     /// @param newAssetProxy Address of new asset proxy to register, or 0x0 to unset assetProxyId.
     /// @param oldAssetProxy Existing asset proxy to overwrite, or 0x0 if assetProxyId is currently unused.
     function registerAssetProxy(
-        uint8 assetProxyId,
+        bytes4 assetProxyId,
         address newAssetProxy,
         address oldAssetProxy
     )
@@ -35,7 +35,7 @@ contract IAssetProxyDispatcher {
     /// @dev Gets an asset proxy.
     /// @param assetProxyId Id of the asset proxy.
     /// @return The asset proxy registered to assetProxyId. Returns 0x0 if no proxy is registered.
-    function getAssetProxy(uint8 assetProxyId)
+    function getAssetProxy(bytes4 assetProxyId)
         external
         view
         returns (address);
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibConstants.sol b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibConstants.sol
index 4a9452448..488ca956c 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibConstants.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibConstants.sol
@@ -25,9 +25,6 @@ contract LibConstants {
     //        not constant to make testing easier.
     bytes public ZRX_ASSET_DATA;
 
-    // Proxy Id for ZRX token.
-    uint8 constant ZRX_PROXY_ID = 1;
-
     // @TODO: Remove when we deploy.
     constructor (bytes memory zrxAssetData)
         public
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol
index a43f0f927..e37f41ada 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibExchangeErrors.sol
@@ -18,7 +18,10 @@
 
 pragma solidity ^0.4.24;
 
+/// @dev This contract documents the revert reasons used in the Exchange contract.
+/// This contract is intended to serve as a reference, but is not actually used for efficiency reasons.
 contract LibExchangeErrors {
+
     /// Order validation errors ///
     string constant ORDER_UNFILLABLE = "ORDER_UNFILLABLE";                              // Order cannot be filled.
     string constant INVALID_MAKER = "INVALID_MAKER";                                    // Invalid makerAddress.
@@ -56,9 +59,11 @@ contract LibExchangeErrors {
 
     /// dispatchTransferFrom errors ///
     string constant ASSET_PROXY_DOES_NOT_EXIST = "ASSET_PROXY_DOES_NOT_EXIST";          // No assetProxy registered at given id.
+    string constant TRANSFER_FAILED = "TRANSFER_FAILED";                                // Asset transfer unsuccesful.
 
     /// Length validation errors ///
     string constant LENGTH_GREATER_THAN_0_REQUIRED = "LENGTH_GREATER_THAN_0_REQUIRED";  // Byte array must have a length greater than 0.
+    string constant LENGTH_GREATER_THAN_3_REQUIRED = "LENGTH_GREATER_THAN_3_REQUIRED";  // Byte array must have a length greater than 3.
     string constant LENGTH_0_REQUIRED = "LENGTH_0_REQUIRED";                            // Byte array must have a length of 0.
     string constant LENGTH_65_REQUIRED = "LENGTH_65_REQUIRED";                          // Byte array must have a length of 65.
 }
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibMath.sol b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibMath.sol
index 233547b9f..bfe2fd33f 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibMath.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/libs/LibMath.sol
@@ -23,7 +23,6 @@ import "../../../utils/SafeMath/SafeMath.sol";
 contract LibMath is
     SafeMath
 {
-    string constant ROUNDING_ERROR_ON_PARTIAL_AMOUNT = "A rounding error occurred when calculating partial transfer amounts.";
 
     /// @dev Calculates partial value given a numerator and denominator.
     /// @param numerator Numerator.
diff --git a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
index 788f42c60..c2b506dcf 100644
--- a/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol
@@ -27,20 +27,18 @@ contract MAssetProxyDispatcher is
 
     // Logs registration of new asset proxy
     event AssetProxySet(
-        uint8 id,               // Id of new registered AssetProxy.
+        bytes4 id,              // Id of new registered AssetProxy.
         address newAssetProxy,  // Address of new registered AssetProxy.
         address oldAssetProxy   // Address of AssetProxy that was overwritten at given id (or null address).
     );
 
     /// @dev Forwards arguments to assetProxy and calls `transferFrom`. Either succeeds or throws.
-    /// @param assetData Byte array encoded for the respective asset proxy.
-    /// @param assetProxyId Id of assetProxy to dispach to.
+    /// @param assetData Byte array encoded for the asset.
     /// @param from Address to transfer token from.
     /// @param to Address to transfer token to.
     /// @param amount Amount of token to transfer.
     function dispatchTransferFrom(
         bytes memory assetData,
-        uint8 assetProxyId,
         address from,
         address to,
         uint256 amount
diff --git a/packages/contracts/src/contracts/current/test/DummyERC721Token/DummyERC721Token.sol b/packages/contracts/src/contracts/current/test/DummyERC721Token/DummyERC721Token.sol
index 5503eb2f2..78ea96447 100644
--- a/packages/contracts/src/contracts/current/test/DummyERC721Token/DummyERC721Token.sol
+++ b/packages/contracts/src/contracts/current/test/DummyERC721Token/DummyERC721Token.sol
@@ -56,4 +56,20 @@ contract DummyERC721Token is
         );
         _mint(to, tokenId);
     }
+
+    /**
+    * @dev Function to burn a token
+    * @dev Reverts if the given token ID doesn't exist
+    * @param tokenId uint256 ID of the token to be minted by the msg.sender
+    */
+    function burn(address owner, uint256 tokenId)
+        public
+        onlyOwner
+    {
+        require(
+            exists(tokenId),
+            "Token with tokenId does not exist."
+        );
+        _burn(owner, tokenId);
+    }
 }
diff --git a/packages/contracts/src/contracts/current/test/TestAssetDataDecoders/TestAssetDataDecoders.sol b/packages/contracts/src/contracts/current/test/TestAssetDataDecoders/TestAssetDataDecoders.sol
deleted file mode 100644
index 5987291d2..000000000
--- a/packages/contracts/src/contracts/current/test/TestAssetDataDecoders/TestAssetDataDecoders.sol
+++ /dev/null
@@ -1,56 +0,0 @@
-/*
-
-  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 "../../protocol/AssetProxy/ERC20Proxy.sol";
-import "../../protocol/AssetProxy/ERC721Proxy.sol";
-
-contract TestAssetDataDecoders is
-    ERC721Proxy
-{
-    /// @dev Decodes ERC721 Asset data.
-    /// @param assetData Encoded byte array.
-    /// @return proxyId Intended ERC721 proxy id.
-    /// @return token ERC721 token address.
-    /// @return tokenId ERC721 token id.
-    /// @return receiverData Additional data with no specific format, which
-    ///                      is passed to the receiving contract's onERC721Received.
-    function publicDecodeERC721Data(bytes memory assetData)
-        public
-        pure
-        returns (
-            address token,
-            uint256 tokenId,
-            bytes memory receiverData
-        )
-    {
-        (
-            token,
-            tokenId,
-            receiverData
-        ) = decodeERC721AssetData(assetData);
-
-        return (
-            token,
-            tokenId,
-            receiverData
-        );
-    }
-}
diff --git a/packages/contracts/src/contracts/current/test/TestAssetProxyDispatcher/TestAssetProxyDispatcher.sol b/packages/contracts/src/contracts/current/test/TestAssetProxyDispatcher/TestAssetProxyDispatcher.sol
index d469a07f0..2ae69e0ef 100644
--- a/packages/contracts/src/contracts/current/test/TestAssetProxyDispatcher/TestAssetProxyDispatcher.sol
+++ b/packages/contracts/src/contracts/current/test/TestAssetProxyDispatcher/TestAssetProxyDispatcher.sol
@@ -24,12 +24,11 @@ import "../../protocol/Exchange/MixinAssetProxyDispatcher.sol";
 contract TestAssetProxyDispatcher is MixinAssetProxyDispatcher {
     function publicDispatchTransferFrom(
         bytes memory assetData,
-        uint8 assetProxyId,
         address from,
         address to,
         uint256 amount)
         public
     {
-        dispatchTransferFrom(assetData, assetProxyId, from, to, amount);
+        dispatchTransferFrom(assetData, from, to, amount);
     }
 }
diff --git a/packages/contracts/src/contracts/current/test/Whitelist/Whitelist.sol b/packages/contracts/src/contracts/current/test/Whitelist/Whitelist.sol
index d35815474..8b52858b1 100644
--- a/packages/contracts/src/contracts/current/test/Whitelist/Whitelist.sol
+++ b/packages/contracts/src/contracts/current/test/Whitelist/Whitelist.sol
@@ -23,13 +23,13 @@ import "../../protocol/Exchange/interfaces/IExchange.sol";
 import "../../protocol/Exchange/libs/LibOrder.sol";
 import "../../utils/Ownable/Ownable.sol";
 
-contract Whitelist is 
+contract Whitelist is
     Ownable
 {
     // Revert reasons
-    string constant MAKER_NOT_WHITELISTED = "Maker address not whitelisted.";
-    string constant TAKER_NOT_WHITELISTED = "Taker address not whitelisted.";
-    string constant INVALID_SENDER = "Sender must equal transaction origin.";
+    string constant MAKER_NOT_WHITELISTED = "MAKER_NOT_WHITELISTED"; // Maker address not whitelisted.
+    string constant TAKER_NOT_WHITELISTED = "TAKER_NOT_WHITELISTED"; // Taker address not whitelisted.
+    string constant INVALID_SENDER = "INVALID_SENDER"; // Sender must equal transaction origin.
 
     // Mapping of address => whitelist status.
     mapping (address => bool) public isWhitelisted;
@@ -77,7 +77,7 @@ contract Whitelist is
         public
     {
         address takerAddress = msg.sender;
-    
+
         // This contract must be the entry point for the transaction.
         require(
             takerAddress == tx.origin,
diff --git a/packages/contracts/src/contracts/current/tokens/ERC20Token/ERC20Token.sol b/packages/contracts/src/contracts/current/tokens/ERC20Token/ERC20Token.sol
index f0bcdafef..b6961a6ec 100644
--- a/packages/contracts/src/contracts/current/tokens/ERC20Token/ERC20Token.sol
+++ b/packages/contracts/src/contracts/current/tokens/ERC20Token/ERC20Token.sol
@@ -23,8 +23,8 @@ import "./IERC20Token.sol";
 
 contract ERC20Token is IERC20Token {
 
-    string constant INSUFFICIENT_BALANCE = "Insufficient balance to complete transfer.";
-    string constant INSUFFICIENT_ALLOWANCE = "Insufficient allowance to complete transfer.";
+    string constant INSUFFICIENT_BALANCE = "ERC20_INSUFFICIENT_BALANCE";
+    string constant INSUFFICIENT_ALLOWANCE = "ERC20_INSUFFICIENT_ALLOWANCE";
     string constant OVERFLOW = "Transfer would result in an overflow.";
 
     mapping (address => uint256) balances;
@@ -97,4 +97,3 @@ contract ERC20Token is IERC20Token {
         return allowed[_owner][_spender];
     }
 }
-
diff --git a/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol b/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
index e4cbf318b..78b1ddf7c 100644
--- a/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
+++ b/packages/contracts/src/contracts/current/utils/LibBytes/LibBytes.sol
@@ -19,17 +19,8 @@
 pragma solidity ^0.4.24;
 
 library LibBytes {
-    using LibBytes for bytes;
 
-    // Revert reasons
-    string constant GREATER_THAN_ZERO_LENGTH_REQUIRED = "GREATER_THAN_ZERO_LENGTH_REQUIRED";
-    string constant GREATER_OR_EQUAL_TO_4_LENGTH_REQUIRED = "GREATER_OR_EQUAL_TO_4_LENGTH_REQUIRED";
-    string constant GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED = "GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED";
-    string constant GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED = "GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED";
-    string constant GREATER_OR_EQUAL_TO_NESTED_BYTES_LENGTH_REQUIRED = "GREATER_OR_EQUAL_TO_NESTED_BYTES_LENGTH_REQUIRED";
-    string constant GREATER_OR_EQUAL_TO_SOURCE_BYTES_LENGTH_REQUIRED = "GREATER_OR_EQUAL_TO_SOURCE_BYTES_LENGTH_REQUIRED";
-    string constant FROM_LESS_THAN_TO_REQUIRED = "FROM_LESS_THAN_TO_REQUIRED";
-    string constant TO_LESS_THAN_LENGTH_REQUIRED = "TO_LESS_THAN_LENGTH_REQUIRED";
+    using LibBytes for bytes;
 
     /// @dev Gets the memory address for a byte array.
     /// @param input Byte array to lookup.
@@ -176,8 +167,14 @@ library LibBytes {
         pure
         returns (bytes memory result)
     {
-        require(from <= to, FROM_LESS_THAN_TO_REQUIRED);
-        require(to < b.length, TO_LESS_THAN_LENGTH_REQUIRED);
+        require(
+            from <= to,
+            "FROM_LESS_THAN_TO_REQUIRED"
+        );
+        require(
+            to < b.length,
+            "TO_LESS_THAN_LENGTH_REQUIRED"
+        );
         
         // Create a new bytes structure and copy contents
         result = new bytes(to - from);
@@ -199,8 +196,14 @@ library LibBytes {
         pure
         returns (bytes memory result)
     {
-        require(from <= to, FROM_LESS_THAN_TO_REQUIRED);
-        require(to < b.length, TO_LESS_THAN_LENGTH_REQUIRED);
+        require(
+            from <= to,
+            "FROM_LESS_THAN_TO_REQUIRED"
+        );
+        require(
+            to < b.length,
+            "TO_LESS_THAN_LENGTH_REQUIRED"
+        );
         
         // Create a new bytes structure around [from, to) in-place.
         assembly {
@@ -220,7 +223,7 @@ library LibBytes {
     {
         require(
             b.length > 0,
-            GREATER_THAN_ZERO_LENGTH_REQUIRED
+            "GREATER_THAN_ZERO_LENGTH_REQUIRED"
         );
 
         // Store last byte.
@@ -244,7 +247,7 @@ library LibBytes {
     {
         require(
             b.length >= 20,
-            GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED
+            "GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED"
         );
 
         // Store last 20 bytes.
@@ -290,7 +293,7 @@ library LibBytes {
     {
         require(
             b.length >= index + 20,  // 20 is length of address
-            GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED
+            "GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED"
         );
 
         // Add offset to index:
@@ -322,7 +325,7 @@ library LibBytes {
     {
         require(
             b.length >= index + 20,  // 20 is length of address
-            GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED
+            "GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED"
         );
 
         // Add offset to index:
@@ -365,7 +368,7 @@ library LibBytes {
     {
         require(
             b.length >= index + 32,
-            GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED
+            "GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED"
         );
 
         // Arrays are prefixed by a 256 bit length parameter
@@ -392,7 +395,7 @@ library LibBytes {
     {
         require(
             b.length >= index + 32,
-            GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED
+            "GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED"
         );
 
         // Arrays are prefixed by a 256 bit length parameter
@@ -447,7 +450,7 @@ library LibBytes {
     {
         require(
             b.length >= index + 4,
-            GREATER_OR_EQUAL_TO_4_LENGTH_REQUIRED
+            "GREATER_OR_EQUAL_TO_4_LENGTH_REQUIRED"
         );
         assembly {
             result := mload(add(b, 32))
@@ -459,6 +462,8 @@ library LibBytes {
     }
 
     /// @dev Reads nested bytes from a specific position.
+    /// @dev NOTE: the returned value overlaps with the input value.
+    ///            Both should be treated as immutable.
     /// @param b Byte array containing nested bytes.
     /// @param index Index of nested bytes.
     /// @return result Nested bytes.
@@ -478,17 +483,13 @@ library LibBytes {
         // length of nested bytes
         require(
             b.length >= index + nestedBytesLength,
-            GREATER_OR_EQUAL_TO_NESTED_BYTES_LENGTH_REQUIRED
+            "GREATER_OR_EQUAL_TO_NESTED_BYTES_LENGTH_REQUIRED"
         );
-
-        // Allocate memory and copy value to result
-        result = new bytes(nestedBytesLength);
-        memCopy(
-            result.contentAddress(),
-            b.contentAddress() + index,
-            nestedBytesLength
-        );
-
+        
+        // Return a pointer to the byte array as it exists inside `b`
+        assembly {
+            result := add(b, index)
+        }
         return result;
     }
 
@@ -508,7 +509,7 @@ library LibBytes {
         // length of input
         require(
             b.length >= index + 32 /* 32 bytes to store length */ + input.length,
-            GREATER_OR_EQUAL_TO_NESTED_BYTES_LENGTH_REQUIRED
+            "GREATER_OR_EQUAL_TO_NESTED_BYTES_LENGTH_REQUIRED"
         );
 
         // Copy <input> into <b>
@@ -533,7 +534,7 @@ library LibBytes {
         // Dest length must be >= source length, or some bytes would not be copied.
         require(
             dest.length >= sourceLen,
-            GREATER_OR_EQUAL_TO_SOURCE_BYTES_LENGTH_REQUIRED
+            "GREATER_OR_EQUAL_TO_SOURCE_BYTES_LENGTH_REQUIRED"
         );
         memCopy(
             dest.contentAddress(),
diff --git a/packages/contracts/src/contracts/current/utils/Ownable/Ownable.sol b/packages/contracts/src/contracts/current/utils/Ownable/Ownable.sol
index 99b93d0d2..6f5761cc7 100644
--- a/packages/contracts/src/contracts/current/utils/Ownable/Ownable.sol
+++ b/packages/contracts/src/contracts/current/utils/Ownable/Ownable.sol
@@ -13,9 +13,6 @@ import "./IOwnable.sol";
 contract Ownable is IOwnable {
     address public owner;
 
-    // Revert reasons
-    string constant ONLY_CONTRACT_OWNER = "ONLY_CONTRACT_OWNER";
-
     constructor ()
         public
     {
@@ -25,7 +22,7 @@ contract Ownable is IOwnable {
     modifier onlyOwner() {
         require(
             msg.sender == owner,
-            ONLY_CONTRACT_OWNER
+            "ONLY_CONTRACT_OWNER"
         );
         _;
     }
diff --git a/packages/contracts/src/utils/artifacts.ts b/packages/contracts/src/utils/artifacts.ts
index a46bab9ae..d58e7973c 100644
--- a/packages/contracts/src/utils/artifacts.ts
+++ b/packages/contracts/src/utils/artifacts.ts
@@ -11,7 +11,6 @@ import * as ExchangeWrapper from '../artifacts/ExchangeWrapper.json';
 import * as MixinAuthorizable from '../artifacts/MixinAuthorizable.json';
 import * as MultiSigWallet from '../artifacts/MultiSigWallet.json';
 import * as MultiSigWalletWithTimeLock from '../artifacts/MultiSigWalletWithTimeLock.json';
-import * as TestAssetDataDecoders from '../artifacts/TestAssetDataDecoders.json';
 import * as TestAssetProxyDispatcher from '../artifacts/TestAssetProxyDispatcher.json';
 import * as TestAssetProxyOwner from '../artifacts/TestAssetProxyOwner.json';
 import * as TestLibBytes from '../artifacts/TestLibBytes.json';
@@ -39,7 +38,6 @@ export const artifacts = {
     MultiSigWalletWithTimeLock: (MultiSigWalletWithTimeLock as any) as ContractArtifact,
     TestAssetProxyOwner: (TestAssetProxyOwner as any) as ContractArtifact,
     TestAssetProxyDispatcher: (TestAssetProxyDispatcher as any) as ContractArtifact,
-    TestAssetDataDecoders: (TestAssetDataDecoders as any) as ContractArtifact,
     TestLibBytes: (TestLibBytes as any) as ContractArtifact,
     TestLibs: (TestLibs as any) as ContractArtifact,
     TestSignatureValidator: (TestSignatureValidator as any) as ContractArtifact,
diff --git a/packages/contracts/src/utils/assertions.ts b/packages/contracts/src/utils/assertions.ts
index 615e648f3..e702a3200 100644
--- a/packages/contracts/src/utils/assertions.ts
+++ b/packages/contracts/src/utils/assertions.ts
@@ -1,3 +1,4 @@
+import { RevertReason } from '@0xproject/types';
 import * as chai from 'chai';
 import * as _ from 'lodash';
 
@@ -52,6 +53,21 @@ export function expectRevertOrAlwaysFailingTransactionAsync<T>(p: Promise<T>): P
 }
 
 /**
+ * Rejects if the given Promise does not reject with the given revert reason or "always
+ * failing transaction" error.
+ * @param p the Promise which is expected to reject
+ * @param reason a specific revert reason
+ * @returns a new Promise which will reject if the conditions are not met and
+ * otherwise resolve with no value.
+ */
+export function expectRevertReasonOrAlwaysFailingTransactionAsync<T>(
+    p: Promise<T>,
+    reason: RevertReason,
+): PromiseLike<void> {
+    return _expectEitherErrorAsync(p, 'always failing transaction', reason);
+}
+
+/**
  * Rejects if the given Promise does not reject with a "revert" or "Contract
  * call failed" error.
  * @param p the Promise which is expected to reject
diff --git a/packages/contracts/src/utils/asset_wrapper.ts b/packages/contracts/src/utils/asset_wrapper.ts
new file mode 100644
index 000000000..a7f91f413
--- /dev/null
+++ b/packages/contracts/src/utils/asset_wrapper.ts
@@ -0,0 +1,217 @@
+import { assetProxyUtils } from '@0xproject/order-utils';
+import { AssetProxyId } from '@0xproject/types';
+import { BigNumber, errorUtils } from '@0xproject/utils';
+import * as _ from 'lodash';
+
+import { AbstractAssetWrapper } from '../abstract/abstract_asset_wrapper';
+
+import { constants } from './constants';
+import { ERC20Wrapper } from './erc20_wrapper';
+import { ERC721Wrapper } from './erc721_wrapper';
+
+interface ProxyIdToAssetWrappers {
+    [proxyId: string]: AbstractAssetWrapper;
+}
+
+/**
+ * This class abstracts away the differences between ERC20 and ERC721 tokens so that
+ * the logic that uses it does not need to care what standard a token belongs to.
+ */
+export class AssetWrapper {
+    private _proxyIdToAssetWrappers: ProxyIdToAssetWrappers;
+    constructor(assetWrappers: AbstractAssetWrapper[]) {
+        this._proxyIdToAssetWrappers = {};
+        _.each(assetWrappers, assetWrapper => {
+            const proxyId = assetWrapper.getProxyId();
+            this._proxyIdToAssetWrappers[proxyId] = assetWrapper;
+        });
+    }
+    public async getBalanceAsync(userAddress: string, assetData: string): Promise<BigNumber> {
+        const proxyId = assetProxyUtils.decodeAssetDataId(assetData);
+        switch (proxyId) {
+            case AssetProxyId.ERC20: {
+                const erc20Wrapper = this._proxyIdToAssetWrappers[proxyId] as ERC20Wrapper;
+                const balance = await erc20Wrapper.getBalanceAsync(userAddress, assetData);
+                return balance;
+            }
+            case AssetProxyId.ERC721: {
+                const assetWrapper = this._proxyIdToAssetWrappers[proxyId] as ERC721Wrapper;
+                const assetProxyData = assetProxyUtils.decodeERC721AssetData(assetData);
+                const isOwner = await assetWrapper.isOwnerAsync(
+                    userAddress,
+                    assetProxyData.tokenAddress,
+                    assetProxyData.tokenId,
+                );
+                const balance = isOwner ? new BigNumber(1) : new BigNumber(0);
+                return balance;
+            }
+            default:
+                throw errorUtils.spawnSwitchErr('proxyId', proxyId);
+        }
+    }
+    public async setBalanceAsync(userAddress: string, assetData: string, desiredBalance: BigNumber): Promise<void> {
+        const proxyId = assetProxyUtils.decodeAssetDataId(assetData);
+        switch (proxyId) {
+            case AssetProxyId.ERC20: {
+                const erc20Wrapper = this._proxyIdToAssetWrappers[proxyId] as ERC20Wrapper;
+                await erc20Wrapper.setBalanceAsync(userAddress, assetData, desiredBalance);
+                return;
+            }
+            case AssetProxyId.ERC721: {
+                if (!desiredBalance.eq(0) && !desiredBalance.eq(1)) {
+                    throw new Error(`Balance for ERC721 token can only be set to 0 or 1. Got: ${desiredBalance}`);
+                }
+                const erc721Wrapper = this._proxyIdToAssetWrappers[proxyId] as ERC721Wrapper;
+                const assetProxyData = assetProxyUtils.decodeERC721AssetData(assetData);
+                const doesTokenExist = erc721Wrapper.doesTokenExistAsync(
+                    assetProxyData.tokenAddress,
+                    assetProxyData.tokenId,
+                );
+                if (!doesTokenExist && desiredBalance.eq(1)) {
+                    await erc721Wrapper.mintAsync(assetProxyData.tokenAddress, assetProxyData.tokenId, userAddress);
+                    return;
+                } else if (!doesTokenExist && desiredBalance.eq(0)) {
+                    return; // noop
+                }
+                const tokenOwner = await erc721Wrapper.ownerOfAsync(
+                    assetProxyData.tokenAddress,
+                    assetProxyData.tokenId,
+                );
+                if (userAddress !== tokenOwner && desiredBalance.eq(1)) {
+                    await erc721Wrapper.transferFromAsync(
+                        assetProxyData.tokenAddress,
+                        assetProxyData.tokenId,
+                        tokenOwner,
+                        userAddress,
+                    );
+                } else if (tokenOwner === userAddress && desiredBalance.eq(0)) {
+                    // Burn token
+                    await erc721Wrapper.burnAsync(assetProxyData.tokenAddress, assetProxyData.tokenId, userAddress);
+                    return;
+                } else if (
+                    (userAddress !== tokenOwner && desiredBalance.eq(0)) ||
+                    (tokenOwner === userAddress && desiredBalance.eq(1))
+                ) {
+                    return; // noop
+                }
+                break;
+            }
+            default:
+                throw errorUtils.spawnSwitchErr('proxyId', proxyId);
+        }
+    }
+    public async getProxyAllowanceAsync(userAddress: string, assetData: string): Promise<BigNumber> {
+        const proxyId = assetProxyUtils.decodeAssetDataId(assetData);
+        switch (proxyId) {
+            case AssetProxyId.ERC20: {
+                const erc20Wrapper = this._proxyIdToAssetWrappers[proxyId] as ERC20Wrapper;
+                const allowance = await erc20Wrapper.getProxyAllowanceAsync(userAddress, assetData);
+                return allowance;
+            }
+            case AssetProxyId.ERC721: {
+                const assetWrapper = this._proxyIdToAssetWrappers[proxyId] as ERC721Wrapper;
+                const erc721ProxyData = assetProxyUtils.decodeERC721AssetData(assetData);
+                const isProxyApprovedForAll = await assetWrapper.isProxyApprovedForAllAsync(
+                    userAddress,
+                    erc721ProxyData.tokenAddress,
+                );
+                if (isProxyApprovedForAll) {
+                    return constants.UNLIMITED_ALLOWANCE_IN_BASE_UNITS;
+                }
+
+                const isProxyApproved = await assetWrapper.isProxyApprovedAsync(
+                    erc721ProxyData.tokenAddress,
+                    erc721ProxyData.tokenId,
+                );
+                const allowance = isProxyApproved ? new BigNumber(1) : new BigNumber(0);
+                return allowance;
+            }
+            default:
+                throw errorUtils.spawnSwitchErr('proxyId', proxyId);
+        }
+    }
+    public async setProxyAllowanceAsync(
+        userAddress: string,
+        assetData: string,
+        desiredAllowance: BigNumber,
+    ): Promise<void> {
+        const proxyId = assetProxyUtils.decodeAssetDataId(assetData);
+        switch (proxyId) {
+            case AssetProxyId.ERC20: {
+                const erc20Wrapper = this._proxyIdToAssetWrappers[proxyId] as ERC20Wrapper;
+                await erc20Wrapper.setAllowanceAsync(userAddress, assetData, desiredAllowance);
+                return;
+            }
+            case AssetProxyId.ERC721: {
+                if (
+                    !desiredAllowance.eq(0) &&
+                    !desiredAllowance.eq(1) &&
+                    !desiredAllowance.eq(constants.UNLIMITED_ALLOWANCE_IN_BASE_UNITS)
+                ) {
+                    throw new Error(
+                        `Allowance for ERC721 token can only be set to 0, 1 or 2^256-1. Got: ${desiredAllowance}`,
+                    );
+                }
+                const erc721Wrapper = this._proxyIdToAssetWrappers[proxyId] as ERC721Wrapper;
+                const assetProxyData = assetProxyUtils.decodeERC721AssetData(assetData);
+
+                const doesTokenExist = await erc721Wrapper.doesTokenExistAsync(
+                    assetProxyData.tokenAddress,
+                    assetProxyData.tokenId,
+                );
+                if (!doesTokenExist) {
+                    throw new Error(
+                        `Cannot setProxyAllowance on non-existent token: ${assetProxyData.tokenAddress} ${
+                            assetProxyData.tokenId
+                        }`,
+                    );
+                }
+                const isProxyApprovedForAll = await erc721Wrapper.isProxyApprovedForAllAsync(
+                    userAddress,
+                    assetProxyData.tokenAddress,
+                );
+                if (!isProxyApprovedForAll && desiredAllowance.eq(constants.UNLIMITED_ALLOWANCE_IN_BASE_UNITS)) {
+                    const isApproved = true;
+                    await erc721Wrapper.approveProxyForAllAsync(
+                        assetProxyData.tokenAddress,
+                        assetProxyData.tokenId,
+                        isApproved,
+                    );
+                } else if (isProxyApprovedForAll && desiredAllowance.eq(0)) {
+                    const isApproved = false;
+                    await erc721Wrapper.approveProxyForAllAsync(
+                        assetProxyData.tokenAddress,
+                        assetProxyData.tokenId,
+                        isApproved,
+                    );
+                } else if (isProxyApprovedForAll && desiredAllowance.eq(constants.UNLIMITED_ALLOWANCE_IN_BASE_UNITS)) {
+                    return; // Noop
+                }
+
+                const isProxyApproved = await erc721Wrapper.isProxyApprovedAsync(
+                    assetProxyData.tokenAddress,
+                    assetProxyData.tokenId,
+                );
+                if (!isProxyApproved && desiredAllowance.eq(1)) {
+                    await erc721Wrapper.approveProxyAsync(assetProxyData.tokenAddress, assetProxyData.tokenId);
+                } else if (isProxyApproved && desiredAllowance.eq(0)) {
+                    // Remove approval
+                    await erc721Wrapper.approveAsync(
+                        constants.NULL_ADDRESS,
+                        assetProxyData.tokenAddress,
+                        assetProxyData.tokenId,
+                    );
+                } else if (
+                    (!isProxyApproved && desiredAllowance.eq(0)) ||
+                    (isProxyApproved && desiredAllowance.eq(1))
+                ) {
+                    return; // noop
+                }
+
+                break;
+            }
+            default:
+                throw errorUtils.spawnSwitchErr('proxyId', proxyId);
+        }
+    }
+}
diff --git a/packages/contracts/src/utils/constants.ts b/packages/contracts/src/utils/constants.ts
index f21b8c7a0..2b2bd2425 100644
--- a/packages/contracts/src/utils/constants.ts
+++ b/packages/contracts/src/utils/constants.ts
@@ -19,19 +19,6 @@ const TESTRPC_PRIVATE_KEYS_STRINGS = [
 export const constants = {
     INVALID_OPCODE: 'invalid opcode',
     REVERT: 'revert',
-    LIB_BYTES_GREATER_THAN_ZERO_LENGTH_REQUIRED: 'GREATER_THAN_ZERO_LENGTH_REQUIRED',
-    LIB_BYTES_GREATER_OR_EQUAL_TO_4_LENGTH_REQUIRED: 'GREATER_OR_EQUAL_TO_4_LENGTH_REQUIRED',
-    LIB_BYTES_GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED: 'GREATER_OR_EQUAL_TO_20_LENGTH_REQUIRED',
-    LIB_BYTES_GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED: 'GREATER_OR_EQUAL_TO_32_LENGTH_REQUIRED',
-    LIB_BYTES_GREATER_OR_EQUAL_TO_NESTED_BYTES_LENGTH_REQUIRED: 'GREATER_OR_EQUAL_TO_NESTED_BYTES_LENGTH_REQUIRED',
-    LIB_BYTES_GREATER_OR_EQUAL_TO_SOURCE_BYTES_LENGTH_REQUIRED: 'GREATER_OR_EQUAL_TO_SOURCE_BYTES_LENGTH_REQUIRED',
-    ERC20_INSUFFICIENT_BALANCE: 'Insufficient balance to complete transfer.',
-    ERC20_INSUFFICIENT_ALLOWANCE: 'Insufficient allowance to complete transfer.',
-    EXCHANGE_LENGTH_GREATER_THAN_0_REQUIRED: 'LENGTH_GREATER_THAN_0_REQUIRED',
-    EXCHANGE_SIGNATURE_UNSUPPORTED: 'SIGNATURE_UNSUPPORTED',
-    EXCHANGE_SIGNATURE_ILLEGAL: 'SIGNATURE_ILLEGAL',
-    EXCHANGE_LENGTH_0_REQUIRED: 'LENGTH_0_REQUIRED',
-    EXCHANGE_LENGTH_65_REQUIRED: 'LENGTH_65_REQUIRED',
     TESTRPC_NETWORK_ID: 50,
     // Note(albrow): In practice V8 and most other engines limit the minimum
     // interval for setInterval to 10ms. We still set it to 0 here in order to
diff --git a/packages/contracts/src/utils/core_combinatorial_utils.ts b/packages/contracts/src/utils/core_combinatorial_utils.ts
new file mode 100644
index 000000000..5b725fbe3
--- /dev/null
+++ b/packages/contracts/src/utils/core_combinatorial_utils.ts
@@ -0,0 +1,801 @@
+import {
+    assetProxyUtils,
+    BalanceAndProxyAllowanceLazyStore,
+    ExchangeTransferSimulator,
+    orderHashUtils,
+    OrderStateUtils,
+    OrderValidationUtils,
+} from '@0xproject/order-utils';
+import { AssetProxyId, RevertReason, SignatureType, SignedOrder } from '@0xproject/types';
+import { BigNumber, errorUtils, logUtils } from '@0xproject/utils';
+import { Web3Wrapper } from '@0xproject/web3-wrapper';
+import * as chai from 'chai';
+import { LogWithDecodedArgs, Provider, TxData } from 'ethereum-types';
+import * as _ from 'lodash';
+import 'make-promises-safe';
+
+import { ExchangeContract, FillContractEventArgs } from '../generated_contract_wrappers/exchange';
+import { artifacts } from '../utils/artifacts';
+import { expectRevertReasonOrAlwaysFailingTransactionAsync } from '../utils/assertions';
+import { AssetWrapper } from '../utils/asset_wrapper';
+import { chaiSetup } from '../utils/chai_setup';
+import { constants } from '../utils/constants';
+import { ERC20Wrapper } from '../utils/erc20_wrapper';
+import { ERC721Wrapper } from '../utils/erc721_wrapper';
+import { ExchangeWrapper } from '../utils/exchange_wrapper';
+import { OrderFactoryFromScenario } from '../utils/order_factory_from_scenario';
+import { orderUtils } from '../utils/order_utils';
+import { signingUtils } from '../utils/signing_utils';
+import { SimpleAssetBalanceAndProxyAllowanceFetcher } from '../utils/simple_asset_balance_and_proxy_allowance_fetcher';
+import { SimpleOrderFilledCancelledFetcher } from '../utils/simple_order_filled_cancelled_fetcher';
+import {
+    AllowanceAmountScenario,
+    AssetDataScenario,
+    BalanceAmountScenario,
+    ExpirationTimeSecondsScenario,
+    FeeRecipientAddressScenario,
+    FillScenario,
+    OrderAssetAmountScenario,
+    TakerAssetFillAmountScenario,
+    TakerScenario,
+    TraderStateScenario,
+} from '../utils/types';
+
+chaiSetup.configure();
+const expect = chai.expect;
+
+/**
+ * Instantiates a new instance of CoreCombinatorialUtils. Since this method has some
+ * required async setup, a factory method is required.
+ * @param web3Wrapper Web3Wrapper instance
+ * @param txDefaults Default Ethereum tx options
+ * @return CoreCombinatorialUtils instance
+ */
+export async function coreCombinatorialUtilsFactoryAsync(
+    web3Wrapper: Web3Wrapper,
+    txDefaults: Partial<TxData>,
+): Promise<CoreCombinatorialUtils> {
+    const accounts = await web3Wrapper.getAvailableAddressesAsync();
+    const userAddresses = _.slice(accounts, 0, 5);
+    const [ownerAddress, makerAddress, takerAddress] = userAddresses;
+    const makerPrivateKey = constants.TESTRPC_PRIVATE_KEYS[userAddresses.indexOf(makerAddress)];
+
+    const provider = web3Wrapper.getProvider();
+    const erc20Wrapper = new ERC20Wrapper(provider, userAddresses, ownerAddress);
+    const erc721Wrapper = new ERC721Wrapper(provider, userAddresses, ownerAddress);
+
+    const erc20EighteenDecimalTokenCount = 3;
+    const eighteenDecimals = new BigNumber(18);
+    const [
+        erc20EighteenDecimalTokenA,
+        erc20EighteenDecimalTokenB,
+        zrxToken,
+    ] = await erc20Wrapper.deployDummyTokensAsync(erc20EighteenDecimalTokenCount, eighteenDecimals);
+    const zrxAssetData = assetProxyUtils.encodeERC20AssetData(zrxToken.address);
+
+    const erc20FiveDecimalTokenCount = 2;
+    const fiveDecimals = new BigNumber(18);
+    const [erc20FiveDecimalTokenA, erc20FiveDecimalTokenB] = await erc20Wrapper.deployDummyTokensAsync(
+        erc20FiveDecimalTokenCount,
+        fiveDecimals,
+    );
+    const erc20Proxy = await erc20Wrapper.deployProxyAsync();
+    await erc20Wrapper.setBalancesAndAllowancesAsync();
+
+    const [erc721Token] = await erc721Wrapper.deployDummyTokensAsync();
+    const erc721Proxy = await erc721Wrapper.deployProxyAsync();
+    await erc721Wrapper.setBalancesAndAllowancesAsync();
+    const erc721Balances = await erc721Wrapper.getBalancesAsync();
+
+    const assetWrapper = new AssetWrapper([erc20Wrapper, erc721Wrapper]);
+
+    const exchangeContract = await ExchangeContract.deployFrom0xArtifactAsync(
+        artifacts.Exchange,
+        provider,
+        txDefaults,
+        zrxAssetData,
+    );
+    const exchangeWrapper = new ExchangeWrapper(exchangeContract, provider);
+    await exchangeWrapper.registerAssetProxyAsync(AssetProxyId.ERC20, erc20Proxy.address, ownerAddress);
+    await exchangeWrapper.registerAssetProxyAsync(AssetProxyId.ERC721, erc721Proxy.address, ownerAddress);
+
+    await web3Wrapper.awaitTransactionSuccessAsync(
+        await erc20Proxy.addAuthorizedAddress.sendTransactionAsync(exchangeContract.address, {
+            from: ownerAddress,
+        }),
+        constants.AWAIT_TRANSACTION_MINED_MS,
+    );
+    await web3Wrapper.awaitTransactionSuccessAsync(
+        await erc721Proxy.addAuthorizedAddress.sendTransactionAsync(exchangeContract.address, {
+            from: ownerAddress,
+        }),
+        constants.AWAIT_TRANSACTION_MINED_MS,
+    );
+
+    const orderFactory = new OrderFactoryFromScenario(
+        userAddresses,
+        zrxToken.address,
+        [erc20EighteenDecimalTokenA.address, erc20EighteenDecimalTokenB.address],
+        [erc20FiveDecimalTokenA.address, erc20FiveDecimalTokenB.address],
+        erc721Token,
+        erc721Balances,
+        exchangeContract.address,
+    );
+
+    const coreCombinatorialUtils = new CoreCombinatorialUtils(
+        orderFactory,
+        ownerAddress,
+        makerAddress,
+        makerPrivateKey,
+        takerAddress,
+        zrxAssetData,
+        exchangeWrapper,
+        assetWrapper,
+    );
+    return coreCombinatorialUtils;
+}
+
+export class CoreCombinatorialUtils {
+    public orderFactory: OrderFactoryFromScenario;
+    public ownerAddress: string;
+    public makerAddress: string;
+    public makerPrivateKey: Buffer;
+    public takerAddress: string;
+    public zrxAssetData: string;
+    public exchangeWrapper: ExchangeWrapper;
+    public assetWrapper: AssetWrapper;
+    public static generateFillOrderCombinations(): FillScenario[] {
+        const takerScenarios = [TakerScenario.Unspecified];
+        const feeRecipientScenarios = [FeeRecipientAddressScenario.EthUserAddress];
+        const makerAssetAmountScenario = [OrderAssetAmountScenario.Large];
+        const takerAssetAmountScenario = [OrderAssetAmountScenario.Large];
+        const makerFeeScenario = [OrderAssetAmountScenario.Large];
+        const takerFeeScenario = [OrderAssetAmountScenario.Large];
+        const expirationTimeSecondsScenario = [ExpirationTimeSecondsScenario.InFuture];
+        const makerAssetDataScenario = [
+            AssetDataScenario.ERC20FiveDecimals,
+            AssetDataScenario.ERC20NonZRXEighteenDecimals,
+            AssetDataScenario.ERC721,
+            AssetDataScenario.ZRXFeeToken,
+        ];
+        const takerAssetDataScenario = [
+            AssetDataScenario.ERC20FiveDecimals,
+            AssetDataScenario.ERC20NonZRXEighteenDecimals,
+            AssetDataScenario.ERC721,
+            AssetDataScenario.ZRXFeeToken,
+        ];
+        const takerAssetFillAmountScenario = [TakerAssetFillAmountScenario.ExactlyRemainingFillableTakerAssetAmount];
+        const fillScenarioArrays = CoreCombinatorialUtils._getAllCombinations([
+            takerScenarios,
+            feeRecipientScenarios,
+            makerAssetAmountScenario,
+            takerAssetAmountScenario,
+            makerFeeScenario,
+            takerFeeScenario,
+            expirationTimeSecondsScenario,
+            makerAssetDataScenario,
+            takerAssetDataScenario,
+            takerAssetFillAmountScenario,
+        ]);
+
+        const fillScenarios = _.map(fillScenarioArrays, fillScenarioArray => {
+            const fillScenario: FillScenario = {
+                orderScenario: {
+                    takerScenario: fillScenarioArray[0] as TakerScenario,
+                    feeRecipientScenario: fillScenarioArray[1] as FeeRecipientAddressScenario,
+                    makerAssetAmountScenario: fillScenarioArray[2] as OrderAssetAmountScenario,
+                    takerAssetAmountScenario: fillScenarioArray[3] as OrderAssetAmountScenario,
+                    makerFeeScenario: fillScenarioArray[4] as OrderAssetAmountScenario,
+                    takerFeeScenario: fillScenarioArray[5] as OrderAssetAmountScenario,
+                    expirationTimeSecondsScenario: fillScenarioArray[6] as ExpirationTimeSecondsScenario,
+                    makerAssetDataScenario: fillScenarioArray[7] as AssetDataScenario,
+                    takerAssetDataScenario: fillScenarioArray[8] as AssetDataScenario,
+                },
+                takerAssetFillAmountScenario: fillScenarioArray[9] as TakerAssetFillAmountScenario,
+                makerStateScenario: {
+                    traderAssetBalance: BalanceAmountScenario.Higher,
+                    traderAssetAllowance: AllowanceAmountScenario.Higher,
+                    zrxFeeBalance: BalanceAmountScenario.Higher,
+                    zrxFeeAllowance: AllowanceAmountScenario.Higher,
+                },
+                takerStateScenario: {
+                    traderAssetBalance: BalanceAmountScenario.Higher,
+                    traderAssetAllowance: AllowanceAmountScenario.Higher,
+                    zrxFeeBalance: BalanceAmountScenario.Higher,
+                    zrxFeeAllowance: AllowanceAmountScenario.Higher,
+                },
+            };
+            return fillScenario;
+        });
+
+        return fillScenarios;
+    }
+    /**
+     * Recursive implementation of generating all combinations of the supplied
+     * string-containing arrays.
+     */
+    private static _getAllCombinations(arrays: string[][]): string[][] {
+        // Base case
+        if (arrays.length === 1) {
+            const remainingValues = _.map(arrays[0], val => {
+                return [val];
+            });
+            return remainingValues;
+        } else {
+            const result = [];
+            const restOfArrays = arrays.slice(1);
+            const allCombinationsOfRemaining = CoreCombinatorialUtils._getAllCombinations(restOfArrays); // recur with the rest of array
+            // tslint:disable:prefer-for-of
+            for (let i = 0; i < allCombinationsOfRemaining.length; i++) {
+                for (let j = 0; j < arrays[0].length; j++) {
+                    result.push([arrays[0][j], ...allCombinationsOfRemaining[i]]);
+                }
+            }
+            // tslint:enable:prefer-for-of
+            return result;
+        }
+    }
+    constructor(
+        orderFactory: OrderFactoryFromScenario,
+        ownerAddress: string,
+        makerAddress: string,
+        makerPrivateKey: Buffer,
+        takerAddress: string,
+        zrxAssetData: string,
+        exchangeWrapper: ExchangeWrapper,
+        assetWrapper: AssetWrapper,
+    ) {
+        this.orderFactory = orderFactory;
+        this.ownerAddress = ownerAddress;
+        this.makerAddress = makerAddress;
+        this.makerPrivateKey = makerPrivateKey;
+        this.takerAddress = takerAddress;
+        this.zrxAssetData = zrxAssetData;
+        this.exchangeWrapper = exchangeWrapper;
+        this.assetWrapper = assetWrapper;
+    }
+    public async testFillOrderScenarioAsync(
+        provider: Provider,
+        fillScenario: FillScenario,
+        isVerbose: boolean = false,
+    ): Promise<void> {
+        // 1. Generate order
+        const order = this.orderFactory.generateOrder(fillScenario.orderScenario);
+
+        // 2. Sign order
+        const orderHashBuff = orderHashUtils.getOrderHashBuffer(order);
+        const signature = signingUtils.signMessage(orderHashBuff, this.makerPrivateKey, SignatureType.EthSign);
+        const signedOrder = {
+            ...order,
+            signature: `0x${signature.toString('hex')}`,
+        };
+
+        const balanceAndProxyAllowanceFetcher = new SimpleAssetBalanceAndProxyAllowanceFetcher(this.assetWrapper);
+        const orderFilledCancelledFetcher = new SimpleOrderFilledCancelledFetcher(
+            this.exchangeWrapper,
+            this.zrxAssetData,
+        );
+
+        // 3. Figure out fill amount
+        const takerAssetFillAmount = await this._getTakerAssetFillAmountAsync(
+            signedOrder,
+            fillScenario.takerAssetFillAmountScenario,
+            balanceAndProxyAllowanceFetcher,
+            orderFilledCancelledFetcher,
+        );
+
+        // 4. Permutate the maker and taker balance/allowance scenarios
+        await this._modifyTraderStateAsync(
+            fillScenario.makerStateScenario,
+            fillScenario.takerStateScenario,
+            signedOrder,
+            takerAssetFillAmount,
+        );
+
+        // 5. If I fill it by X, what are the resulting balances/allowances/filled amounts expected?
+        const orderValidationUtils = new OrderValidationUtils(orderFilledCancelledFetcher);
+        const lazyStore = new BalanceAndProxyAllowanceLazyStore(balanceAndProxyAllowanceFetcher);
+        const exchangeTransferSimulator = new ExchangeTransferSimulator(lazyStore);
+
+        let fillRevertReasonIfExists;
+        try {
+            await orderValidationUtils.validateFillOrderThrowIfInvalidAsync(
+                exchangeTransferSimulator,
+                provider,
+                signedOrder,
+                takerAssetFillAmount,
+                this.takerAddress,
+                this.zrxAssetData,
+            );
+            if (isVerbose) {
+                logUtils.log(`Expecting fillOrder to succeed.`);
+            }
+        } catch (err) {
+            fillRevertReasonIfExists = err.message;
+            if (isVerbose) {
+                logUtils.log(`Expecting fillOrder to fail with:`);
+                logUtils.log(err);
+            }
+        }
+
+        // 6. Fill the order
+        await this._fillOrderAndAssertOutcomeAsync(
+            signedOrder,
+            takerAssetFillAmount,
+            lazyStore,
+            fillRevertReasonIfExists,
+        );
+    }
+    private async _fillOrderAndAssertOutcomeAsync(
+        signedOrder: SignedOrder,
+        takerAssetFillAmount: BigNumber,
+        lazyStore: BalanceAndProxyAllowanceLazyStore,
+        fillRevertReasonIfExists: RevertReason | undefined,
+    ): Promise<void> {
+        if (!_.isUndefined(fillRevertReasonIfExists)) {
+            return expectRevertReasonOrAlwaysFailingTransactionAsync(
+                this.exchangeWrapper.fillOrderAsync(signedOrder, this.takerAddress, { takerAssetFillAmount }),
+                fillRevertReasonIfExists,
+            );
+        }
+
+        const makerAddress = signedOrder.makerAddress;
+        const makerAssetData = signedOrder.makerAssetData;
+        const takerAssetData = signedOrder.takerAssetData;
+        const feeRecipient = signedOrder.feeRecipientAddress;
+
+        const expMakerAssetBalanceOfMaker = await lazyStore.getBalanceAsync(makerAssetData, makerAddress);
+        const expMakerAssetAllowanceOfMaker = await lazyStore.getProxyAllowanceAsync(makerAssetData, makerAddress);
+        const expTakerAssetBalanceOfMaker = await lazyStore.getBalanceAsync(takerAssetData, makerAddress);
+        const expZRXAssetBalanceOfMaker = await lazyStore.getBalanceAsync(this.zrxAssetData, makerAddress);
+        const expZRXAssetAllowanceOfMaker = await lazyStore.getProxyAllowanceAsync(this.zrxAssetData, makerAddress);
+        const expTakerAssetBalanceOfTaker = await lazyStore.getBalanceAsync(takerAssetData, this.takerAddress);
+        const expTakerAssetAllowanceOfTaker = await lazyStore.getProxyAllowanceAsync(takerAssetData, this.takerAddress);
+        const expMakerAssetBalanceOfTaker = await lazyStore.getBalanceAsync(makerAssetData, this.takerAddress);
+        const expZRXAssetBalanceOfTaker = await lazyStore.getBalanceAsync(this.zrxAssetData, this.takerAddress);
+        const expZRXAssetAllowanceOfTaker = await lazyStore.getProxyAllowanceAsync(
+            this.zrxAssetData,
+            this.takerAddress,
+        );
+        const expZRXAssetBalanceOfFeeRecipient = await lazyStore.getBalanceAsync(this.zrxAssetData, feeRecipient);
+
+        const orderHash = orderHashUtils.getOrderHashHex(signedOrder);
+        const alreadyFilledTakerAmount = await this.exchangeWrapper.getTakerAssetFilledAmountAsync(orderHash);
+        const remainingTakerAmountToFill = signedOrder.takerAssetAmount.minus(alreadyFilledTakerAmount);
+        const expFilledTakerAmount = takerAssetFillAmount.gt(remainingTakerAmountToFill)
+            ? remainingTakerAmountToFill
+            : alreadyFilledTakerAmount.add(takerAssetFillAmount);
+
+        const expFilledMakerAmount = orderUtils.getPartialAmount(
+            expFilledTakerAmount,
+            signedOrder.takerAssetAmount,
+            signedOrder.makerAssetAmount,
+        );
+
+        // - Let's fill the order!
+        const txReceipt = await this.exchangeWrapper.fillOrderAsync(signedOrder, this.takerAddress, {
+            takerAssetFillAmount,
+        });
+
+        const actFilledTakerAmount = await this.exchangeWrapper.getTakerAssetFilledAmountAsync(orderHash);
+        expect(actFilledTakerAmount).to.be.bignumber.equal(expFilledTakerAmount, 'filledTakerAmount');
+
+        expect(txReceipt.logs.length).to.be.equal(1, 'logs length');
+        // tslint:disable-next-line:no-unnecessary-type-assertion
+        const log = txReceipt.logs[0] as LogWithDecodedArgs<FillContractEventArgs>;
+        expect(log.args.makerAddress).to.be.equal(makerAddress, 'log.args.makerAddress');
+        expect(log.args.takerAddress).to.be.equal(this.takerAddress, 'log.args.this.takerAddress');
+        expect(log.args.feeRecipientAddress).to.be.equal(feeRecipient, 'log.args.feeRecipientAddress');
+        expect(log.args.makerAssetFilledAmount).to.be.bignumber.equal(
+            expFilledMakerAmount,
+            'log.args.makerAssetFilledAmount',
+        );
+        expect(log.args.takerAssetFilledAmount).to.be.bignumber.equal(
+            expFilledTakerAmount,
+            'log.args.takerAssetFilledAmount',
+        );
+        const expMakerFeePaid = orderUtils.getPartialAmount(
+            expFilledTakerAmount,
+            signedOrder.takerAssetAmount,
+            signedOrder.makerFee,
+        );
+        expect(log.args.makerFeePaid).to.be.bignumber.equal(expMakerFeePaid, 'log.args.makerFeePaid');
+        const expTakerFeePaid = orderUtils.getPartialAmount(
+            expFilledTakerAmount,
+            signedOrder.takerAssetAmount,
+            signedOrder.takerFee,
+        );
+        expect(log.args.takerFeePaid).to.be.bignumber.equal(expTakerFeePaid, 'logs.args.takerFeePaid');
+        expect(log.args.orderHash).to.be.equal(orderHash, 'log.args.orderHash');
+        expect(log.args.makerAssetData).to.be.equal(makerAssetData, 'log.args.makerAssetData');
+        expect(log.args.takerAssetData).to.be.equal(takerAssetData, 'log.args.takerAssetData');
+
+        const actMakerAssetBalanceOfMaker = await this.assetWrapper.getBalanceAsync(makerAddress, makerAssetData);
+        expect(actMakerAssetBalanceOfMaker).to.be.bignumber.equal(
+            expMakerAssetBalanceOfMaker,
+            'makerAssetBalanceOfMaker',
+        );
+
+        const actMakerAssetAllowanceOfMaker = await this.assetWrapper.getProxyAllowanceAsync(
+            makerAddress,
+            makerAssetData,
+        );
+        expect(actMakerAssetAllowanceOfMaker).to.be.bignumber.equal(
+            expMakerAssetAllowanceOfMaker,
+            'makerAssetAllowanceOfMaker',
+        );
+
+        const actTakerAssetBalanceOfMaker = await this.assetWrapper.getBalanceAsync(makerAddress, takerAssetData);
+        expect(actTakerAssetBalanceOfMaker).to.be.bignumber.equal(
+            expTakerAssetBalanceOfMaker,
+            'takerAssetBalanceOfMaker',
+        );
+
+        const actZRXAssetBalanceOfMaker = await this.assetWrapper.getBalanceAsync(makerAddress, this.zrxAssetData);
+        expect(actZRXAssetBalanceOfMaker).to.be.bignumber.equal(expZRXAssetBalanceOfMaker, 'ZRXAssetBalanceOfMaker');
+
+        const actZRXAssetAllowanceOfMaker = await this.assetWrapper.getProxyAllowanceAsync(
+            makerAddress,
+            this.zrxAssetData,
+        );
+        expect(actZRXAssetAllowanceOfMaker).to.be.bignumber.equal(
+            expZRXAssetAllowanceOfMaker,
+            'ZRXAssetAllowanceOfMaker',
+        );
+
+        const actTakerAssetBalanceOfTaker = await this.assetWrapper.getBalanceAsync(this.takerAddress, takerAssetData);
+        expect(actTakerAssetBalanceOfTaker).to.be.bignumber.equal(
+            expTakerAssetBalanceOfTaker,
+            'TakerAssetBalanceOfTaker',
+        );
+
+        const actTakerAssetAllowanceOfTaker = await this.assetWrapper.getProxyAllowanceAsync(
+            this.takerAddress,
+            takerAssetData,
+        );
+
+        expect(actTakerAssetAllowanceOfTaker).to.be.bignumber.equal(
+            expTakerAssetAllowanceOfTaker,
+            'TakerAssetAllowanceOfTaker',
+        );
+
+        const actMakerAssetBalanceOfTaker = await this.assetWrapper.getBalanceAsync(this.takerAddress, makerAssetData);
+        expect(actMakerAssetBalanceOfTaker).to.be.bignumber.equal(
+            expMakerAssetBalanceOfTaker,
+            'MakerAssetBalanceOfTaker',
+        );
+
+        const actZRXAssetBalanceOfTaker = await this.assetWrapper.getBalanceAsync(this.takerAddress, this.zrxAssetData);
+        expect(actZRXAssetBalanceOfTaker).to.be.bignumber.equal(expZRXAssetBalanceOfTaker, 'ZRXAssetBalanceOfTaker');
+
+        const actZRXAssetAllowanceOfTaker = await this.assetWrapper.getProxyAllowanceAsync(
+            this.takerAddress,
+            this.zrxAssetData,
+        );
+        expect(actZRXAssetAllowanceOfTaker).to.be.bignumber.equal(
+            expZRXAssetAllowanceOfTaker,
+            'ZRXAssetAllowanceOfTaker',
+        );
+
+        const actZRXAssetBalanceOfFeeRecipient = await this.assetWrapper.getBalanceAsync(
+            feeRecipient,
+            this.zrxAssetData,
+        );
+        expect(actZRXAssetBalanceOfFeeRecipient).to.be.bignumber.equal(
+            expZRXAssetBalanceOfFeeRecipient,
+            'ZRXAssetBalanceOfFeeRecipient',
+        );
+    }
+    private async _getTakerAssetFillAmountAsync(
+        signedOrder: SignedOrder,
+        takerAssetFillAmountScenario: TakerAssetFillAmountScenario,
+        balanceAndProxyAllowanceFetcher: SimpleAssetBalanceAndProxyAllowanceFetcher,
+        orderFilledCancelledFetcher: SimpleOrderFilledCancelledFetcher,
+    ): Promise<BigNumber> {
+        const orderStateUtils = new OrderStateUtils(balanceAndProxyAllowanceFetcher, orderFilledCancelledFetcher);
+        const fillableTakerAssetAmount = await orderStateUtils.getMaxFillableTakerAssetAmountAsync(
+            signedOrder,
+            this.takerAddress,
+        );
+
+        let takerAssetFillAmount;
+        switch (takerAssetFillAmountScenario) {
+            case TakerAssetFillAmountScenario.Zero:
+                takerAssetFillAmount = new BigNumber(0);
+                break;
+
+            case TakerAssetFillAmountScenario.ExactlyRemainingFillableTakerAssetAmount:
+                takerAssetFillAmount = fillableTakerAssetAmount;
+                break;
+
+            case TakerAssetFillAmountScenario.GreaterThanRemainingFillableTakerAssetAmount:
+                takerAssetFillAmount = fillableTakerAssetAmount.add(1);
+                break;
+
+            case TakerAssetFillAmountScenario.LessThanRemainingFillableTakerAssetAmount:
+                const takerAssetProxyId = assetProxyUtils.decodeAssetDataId(signedOrder.takerAssetData);
+                const makerAssetProxyId = assetProxyUtils.decodeAssetDataId(signedOrder.makerAssetData);
+                const isEitherAssetERC721 =
+                    takerAssetProxyId === AssetProxyId.ERC721 || makerAssetProxyId === AssetProxyId.ERC721;
+                if (isEitherAssetERC721) {
+                    throw new Error(
+                        'Cannot test `TakerAssetFillAmountScenario.LessThanRemainingFillableTakerAssetAmount` together with ERC721 assets since orders involving ERC721 must always be filled exactly.',
+                    );
+                }
+                takerAssetFillAmount = fillableTakerAssetAmount.div(2).floor();
+                break;
+
+            default:
+                throw errorUtils.spawnSwitchErr('TakerAssetFillAmountScenario', takerAssetFillAmountScenario);
+        }
+
+        return takerAssetFillAmount;
+    }
+    private async _modifyTraderStateAsync(
+        makerStateScenario: TraderStateScenario,
+        takerStateScenario: TraderStateScenario,
+        signedOrder: SignedOrder,
+        takerAssetFillAmount: BigNumber,
+    ): Promise<void> {
+        const makerAssetFillAmount = orderUtils.getPartialAmount(
+            takerAssetFillAmount,
+            signedOrder.takerAssetAmount,
+            signedOrder.makerAssetAmount,
+        );
+        switch (makerStateScenario.traderAssetBalance) {
+            case BalanceAmountScenario.Higher:
+                break; // Noop since this is already the default
+
+            case BalanceAmountScenario.TooLow:
+                if (makerAssetFillAmount.eq(0)) {
+                    throw new Error(`Cannot set makerAssetBalanceOfMaker TooLow if makerAssetFillAmount is 0`);
+                }
+                const tooLowBalance = makerAssetFillAmount.minus(1);
+                await this.assetWrapper.setBalanceAsync(
+                    signedOrder.makerAddress,
+                    signedOrder.makerAssetData,
+                    tooLowBalance,
+                );
+                break;
+
+            case BalanceAmountScenario.Exact:
+                const exactBalance = makerAssetFillAmount;
+                await this.assetWrapper.setBalanceAsync(
+                    signedOrder.makerAddress,
+                    signedOrder.makerAssetData,
+                    exactBalance,
+                );
+                break;
+
+            default:
+                throw errorUtils.spawnSwitchErr(
+                    'makerStateScenario.traderAssetBalance',
+                    makerStateScenario.traderAssetBalance,
+                );
+        }
+
+        const makerFee = orderUtils.getPartialAmount(
+            takerAssetFillAmount,
+            signedOrder.takerAssetAmount,
+            signedOrder.makerFee,
+        );
+        switch (makerStateScenario.zrxFeeBalance) {
+            case BalanceAmountScenario.Higher:
+                break; // Noop since this is already the default
+
+            case BalanceAmountScenario.TooLow:
+                if (makerFee.eq(0)) {
+                    throw new Error(`Cannot set zrxAsserBalanceOfMaker TooLow if makerFee is 0`);
+                }
+                const tooLowBalance = makerFee.minus(1);
+                await this.assetWrapper.setBalanceAsync(signedOrder.makerAddress, this.zrxAssetData, tooLowBalance);
+                break;
+
+            case BalanceAmountScenario.Exact:
+                const exactBalance = makerFee;
+                await this.assetWrapper.setBalanceAsync(signedOrder.makerAddress, this.zrxAssetData, exactBalance);
+                break;
+
+            default:
+                throw errorUtils.spawnSwitchErr('makerStateScenario.zrxFeeBalance', makerStateScenario.zrxFeeBalance);
+        }
+
+        switch (makerStateScenario.traderAssetAllowance) {
+            case AllowanceAmountScenario.Higher:
+                break; // Noop since this is already the default
+
+            case AllowanceAmountScenario.TooLow:
+                const tooLowAllowance = makerAssetFillAmount.minus(1);
+                await this.assetWrapper.setProxyAllowanceAsync(
+                    signedOrder.makerAddress,
+                    signedOrder.makerAssetData,
+                    tooLowAllowance,
+                );
+                break;
+
+            case AllowanceAmountScenario.Exact:
+                const exactAllowance = makerAssetFillAmount;
+                await this.assetWrapper.setProxyAllowanceAsync(
+                    signedOrder.makerAddress,
+                    signedOrder.makerAssetData,
+                    exactAllowance,
+                );
+                break;
+
+            case AllowanceAmountScenario.Unlimited:
+                await this.assetWrapper.setProxyAllowanceAsync(
+                    signedOrder.makerAddress,
+                    signedOrder.makerAssetData,
+                    constants.UNLIMITED_ALLOWANCE_IN_BASE_UNITS,
+                );
+                break;
+
+            default:
+                throw errorUtils.spawnSwitchErr(
+                    'makerStateScenario.traderAssetAllowance',
+                    makerStateScenario.traderAssetAllowance,
+                );
+        }
+
+        switch (makerStateScenario.zrxFeeAllowance) {
+            case AllowanceAmountScenario.Higher:
+                break; // Noop since this is already the default
+
+            case AllowanceAmountScenario.TooLow:
+                const tooLowAllowance = makerFee.minus(1);
+                await this.assetWrapper.setProxyAllowanceAsync(
+                    signedOrder.makerAddress,
+                    this.zrxAssetData,
+                    tooLowAllowance,
+                );
+                break;
+
+            case AllowanceAmountScenario.Exact:
+                const exactAllowance = makerFee;
+                await this.assetWrapper.setProxyAllowanceAsync(
+                    signedOrder.makerAddress,
+                    this.zrxAssetData,
+                    exactAllowance,
+                );
+                break;
+
+            case AllowanceAmountScenario.Unlimited:
+                await this.assetWrapper.setProxyAllowanceAsync(
+                    signedOrder.makerAddress,
+                    this.zrxAssetData,
+                    constants.UNLIMITED_ALLOWANCE_IN_BASE_UNITS,
+                );
+                break;
+
+            default:
+                throw errorUtils.spawnSwitchErr(
+                    'makerStateScenario.zrxFeeAllowance',
+                    makerStateScenario.zrxFeeAllowance,
+                );
+        }
+
+        switch (takerStateScenario.traderAssetBalance) {
+            case BalanceAmountScenario.Higher:
+                break; // Noop since this is already the default
+
+            case BalanceAmountScenario.TooLow:
+                if (takerAssetFillAmount.eq(0)) {
+                    throw new Error(`Cannot set takerAssetBalanceOfTaker TooLow if takerAssetFillAmount is 0`);
+                }
+                const tooLowBalance = takerAssetFillAmount.minus(1);
+                await this.assetWrapper.setBalanceAsync(this.takerAddress, signedOrder.takerAssetData, tooLowBalance);
+                break;
+
+            case BalanceAmountScenario.Exact:
+                const exactBalance = takerAssetFillAmount;
+                await this.assetWrapper.setBalanceAsync(this.takerAddress, signedOrder.takerAssetData, exactBalance);
+                break;
+
+            default:
+                throw errorUtils.spawnSwitchErr(
+                    'takerStateScenario.traderAssetBalance',
+                    takerStateScenario.traderAssetBalance,
+                );
+        }
+
+        const takerFee = orderUtils.getPartialAmount(
+            takerAssetFillAmount,
+            signedOrder.takerAssetAmount,
+            signedOrder.takerFee,
+        );
+        switch (takerStateScenario.zrxFeeBalance) {
+            case BalanceAmountScenario.Higher:
+                break; // Noop since this is already the default
+
+            case BalanceAmountScenario.TooLow:
+                if (takerFee.eq(0)) {
+                    throw new Error(`Cannot set zrxAssetBalanceOfTaker TooLow if takerFee is 0`);
+                }
+                const tooLowBalance = takerFee.minus(1);
+                await this.assetWrapper.setBalanceAsync(this.takerAddress, this.zrxAssetData, tooLowBalance);
+                break;
+
+            case BalanceAmountScenario.Exact:
+                const exactBalance = takerFee;
+                await this.assetWrapper.setBalanceAsync(this.takerAddress, this.zrxAssetData, exactBalance);
+                break;
+
+            default:
+                throw errorUtils.spawnSwitchErr('takerStateScenario.zrxFeeBalance', takerStateScenario.zrxFeeBalance);
+        }
+
+        switch (takerStateScenario.traderAssetAllowance) {
+            case AllowanceAmountScenario.Higher:
+                break; // Noop since this is already the default
+
+            case AllowanceAmountScenario.TooLow:
+                const tooLowAllowance = takerAssetFillAmount.minus(1);
+                await this.assetWrapper.setProxyAllowanceAsync(
+                    this.takerAddress,
+                    signedOrder.takerAssetData,
+                    tooLowAllowance,
+                );
+                break;
+
+            case AllowanceAmountScenario.Exact:
+                const exactAllowance = takerAssetFillAmount;
+                await this.assetWrapper.setProxyAllowanceAsync(
+                    this.takerAddress,
+                    signedOrder.takerAssetData,
+                    exactAllowance,
+                );
+                break;
+
+            case AllowanceAmountScenario.Unlimited:
+                await this.assetWrapper.setProxyAllowanceAsync(
+                    this.takerAddress,
+                    signedOrder.takerAssetData,
+                    constants.UNLIMITED_ALLOWANCE_IN_BASE_UNITS,
+                );
+                break;
+
+            default:
+                throw errorUtils.spawnSwitchErr(
+                    'takerStateScenario.traderAssetAllowance',
+                    takerStateScenario.traderAssetAllowance,
+                );
+        }
+
+        switch (takerStateScenario.zrxFeeAllowance) {
+            case AllowanceAmountScenario.Higher:
+                break; // Noop since this is already the default
+
+            case AllowanceAmountScenario.TooLow:
+                const tooLowAllowance = takerFee.minus(1);
+                await this.assetWrapper.setProxyAllowanceAsync(
+                    signedOrder.takerAddress,
+                    this.zrxAssetData,
+                    tooLowAllowance,
+                );
+                break;
+
+            case AllowanceAmountScenario.Exact:
+                const exactAllowance = takerFee;
+                await this.assetWrapper.setProxyAllowanceAsync(
+                    signedOrder.takerAddress,
+                    this.zrxAssetData,
+                    exactAllowance,
+                );
+                break;
+
+            case AllowanceAmountScenario.Unlimited:
+                await this.assetWrapper.setProxyAllowanceAsync(
+                    signedOrder.takerAddress,
+                    this.zrxAssetData,
+                    constants.UNLIMITED_ALLOWANCE_IN_BASE_UNITS,
+                );
+                break;
+
+            default:
+                throw errorUtils.spawnSwitchErr(
+                    'takerStateScenario.zrxFeeAllowance',
+                    takerStateScenario.zrxFeeAllowance,
+                );
+        }
+    }
+} // tslint:disable:max-file-line-count
diff --git a/packages/contracts/src/utils/erc20_wrapper.ts b/packages/contracts/src/utils/erc20_wrapper.ts
index 91c9d50b7..7f00e2061 100644
--- a/packages/contracts/src/utils/erc20_wrapper.ts
+++ b/packages/contracts/src/utils/erc20_wrapper.ts
@@ -1,3 +1,4 @@
+import { assetProxyUtils } from '@0xproject/order-utils';
 import { BigNumber } from '@0xproject/utils';
 import { Web3Wrapper } from '@0xproject/web3-wrapper';
 import { Provider } from 'ethereum-types';
@@ -18,6 +19,7 @@ export class ERC20Wrapper {
     private _provider: Provider;
     private _dummyTokenContracts: DummyERC20TokenContract[];
     private _proxyContract?: ERC20ProxyContract;
+    private _proxyIdIfExists?: string;
     constructor(provider: Provider, tokenOwnerAddresses: string[], contractOwnerAddress: string) {
         this._dummyTokenContracts = [];
         this._web3Wrapper = new Web3Wrapper(provider);
@@ -25,8 +27,11 @@ export class ERC20Wrapper {
         this._tokenOwnerAddresses = tokenOwnerAddresses;
         this._contractOwnerAddress = contractOwnerAddress;
     }
-    public async deployDummyTokensAsync(): Promise<DummyERC20TokenContract[]> {
-        for (let i = 0; i < constants.NUM_DUMMY_ERC20_TO_DEPLOY; i++) {
+    public async deployDummyTokensAsync(
+        numberToDeploy: number,
+        decimals: BigNumber,
+    ): Promise<DummyERC20TokenContract[]> {
+        for (let i = 0; i < numberToDeploy; i++) {
             this._dummyTokenContracts.push(
                 await DummyERC20TokenContract.deployFrom0xArtifactAsync(
                     artifacts.DummyERC20Token,
@@ -34,7 +39,7 @@ export class ERC20Wrapper {
                     txDefaults,
                     constants.DUMMY_TOKEN_NAME,
                     constants.DUMMY_TOKEN_SYMBOL,
-                    constants.DUMMY_TOKEN_DECIMALS,
+                    decimals,
                     constants.DUMMY_TOKEN_TOTAL_SUPPLY,
                 ),
             );
@@ -47,8 +52,13 @@ export class ERC20Wrapper {
             this._provider,
             txDefaults,
         );
+        this._proxyIdIfExists = await this._proxyContract.getProxyId.callAsync();
         return this._proxyContract;
     }
+    public getProxyId(): string {
+        this._validateProxyContractExistsOrThrow();
+        return this._proxyIdIfExists as string;
+    }
     public async setBalancesAndAllowancesAsync(): Promise<void> {
         this._validateDummyTokenContractsExistOrThrow();
         this._validateProxyContractExistsOrThrow();
@@ -73,6 +83,36 @@ export class ERC20Wrapper {
             }
         }
     }
+    public async getBalanceAsync(userAddress: string, assetData: string): Promise<BigNumber> {
+        const tokenContract = this._getTokenContractFromAssetData(assetData);
+        const balance = new BigNumber(await tokenContract.balanceOf.callAsync(userAddress));
+        return balance;
+    }
+    public async setBalanceAsync(userAddress: string, assetData: string, amount: BigNumber): Promise<void> {
+        const tokenContract = this._getTokenContractFromAssetData(assetData);
+        await this._web3Wrapper.awaitTransactionSuccessAsync(
+            await tokenContract.setBalance.sendTransactionAsync(userAddress, amount, {
+                from: this._contractOwnerAddress,
+            }),
+            constants.AWAIT_TRANSACTION_MINED_MS,
+        );
+    }
+    public async getProxyAllowanceAsync(userAddress: string, assetData: string): Promise<BigNumber> {
+        const tokenContract = this._getTokenContractFromAssetData(assetData);
+        const proxyAddress = (this._proxyContract as ERC20ProxyContract).address;
+        const allowance = new BigNumber(await tokenContract.allowance.callAsync(userAddress, proxyAddress));
+        return allowance;
+    }
+    public async setAllowanceAsync(userAddress: string, assetData: string, amount: BigNumber): Promise<void> {
+        const tokenContract = this._getTokenContractFromAssetData(assetData);
+        const proxyAddress = (this._proxyContract as ERC20ProxyContract).address;
+        await this._web3Wrapper.awaitTransactionSuccessAsync(
+            await tokenContract.approve.sendTransactionAsync(proxyAddress, amount, {
+                from: userAddress,
+            }),
+            constants.AWAIT_TRANSACTION_MINED_MS,
+        );
+    }
     public async getBalancesAsync(): Promise<ERC20BalancesByOwner> {
         this._validateDummyTokenContractsExistOrThrow();
         const balancesByOwner: ERC20BalancesByOwner = {};
@@ -105,6 +145,15 @@ export class ERC20Wrapper {
         const tokenAddresses = _.map(this._dummyTokenContracts, dummyTokenContract => dummyTokenContract.address);
         return tokenAddresses;
     }
+    private _getTokenContractFromAssetData(assetData: string): DummyERC20TokenContract {
+        const erc20ProxyData = assetProxyUtils.decodeERC20AssetData(assetData);
+        const tokenAddress = erc20ProxyData.tokenAddress;
+        const tokenContractIfExists = _.find(this._dummyTokenContracts, c => c.address === tokenAddress);
+        if (_.isUndefined(tokenContractIfExists)) {
+            throw new Error(`Token: ${tokenAddress} was not deployed through ERC20Wrapper`);
+        }
+        return tokenContractIfExists;
+    }
     private _validateDummyTokenContractsExistOrThrow(): void {
         if (_.isUndefined(this._dummyTokenContracts)) {
             throw new Error('Dummy ERC20 tokens not yet deployed, please call "deployDummyTokensAsync"');
diff --git a/packages/contracts/src/utils/erc721_wrapper.ts b/packages/contracts/src/utils/erc721_wrapper.ts
index b20d9acd2..309135ae4 100644
--- a/packages/contracts/src/utils/erc721_wrapper.ts
+++ b/packages/contracts/src/utils/erc721_wrapper.ts
@@ -19,6 +19,7 @@ export class ERC721Wrapper {
     private _provider: Provider;
     private _dummyTokenContracts: DummyERC721TokenContract[];
     private _proxyContract?: ERC721ProxyContract;
+    private _proxyIdIfExists?: string;
     private _initialTokenIdsByOwner: ERC721TokenIdsByOwner = {};
     constructor(provider: Provider, tokenOwnerAddresses: string[], contractOwnerAddress: string) {
         this._web3Wrapper = new Web3Wrapper(provider);
@@ -47,8 +48,13 @@ export class ERC721Wrapper {
             this._provider,
             txDefaults,
         );
+        this._proxyIdIfExists = await this._proxyContract.getProxyId.callAsync();
         return this._proxyContract;
     }
+    public getProxyId(): string {
+        this._validateProxyContractExistsOrThrow();
+        return this._proxyIdIfExists as string;
+    }
     public async setBalancesAndAllowancesAsync(): Promise<void> {
         this._validateDummyTokenContractsExistOrThrow();
         this._validateProxyContractExistsOrThrow();
@@ -57,12 +63,7 @@ export class ERC721Wrapper {
             for (const tokenOwnerAddress of this._tokenOwnerAddresses) {
                 for (let i = 0; i < constants.NUM_ERC721_TOKENS_TO_MINT; i++) {
                     const tokenId = generatePseudoRandomSalt();
-                    await this._web3Wrapper.awaitTransactionSuccessAsync(
-                        await dummyTokenContract.mint.sendTransactionAsync(tokenOwnerAddress, tokenId, {
-                            from: this._contractOwnerAddress,
-                        }),
-                        constants.AWAIT_TRANSACTION_MINED_MS,
-                    );
+                    await this.mintAsync(dummyTokenContract.address, tokenId, tokenOwnerAddress);
                     if (_.isUndefined(this._initialTokenIdsByOwner[tokenOwnerAddress])) {
                         this._initialTokenIdsByOwner[tokenOwnerAddress] = {
                             [dummyTokenContract.address]: [],
@@ -72,19 +73,100 @@ export class ERC721Wrapper {
                         this._initialTokenIdsByOwner[tokenOwnerAddress][dummyTokenContract.address] = [];
                     }
                     this._initialTokenIdsByOwner[tokenOwnerAddress][dummyTokenContract.address].push(tokenId);
+
+                    await this.approveProxyAsync(dummyTokenContract.address, tokenId);
                 }
-                const shouldApprove = true;
-                await this._web3Wrapper.awaitTransactionSuccessAsync(
-                    await dummyTokenContract.setApprovalForAll.sendTransactionAsync(
-                        (this._proxyContract as ERC721ProxyContract).address,
-                        shouldApprove,
-                        { from: tokenOwnerAddress },
-                    ),
-                    constants.AWAIT_TRANSACTION_MINED_MS,
-                );
             }
         }
     }
+    public async doesTokenExistAsync(tokenAddress: string, tokenId: BigNumber): Promise<boolean> {
+        const tokenContract = this._getTokenContractFromAssetData(tokenAddress);
+        const doesExist = await tokenContract.exists.callAsync(tokenId);
+        return doesExist;
+    }
+    public async approveProxyAsync(tokenAddress: string, tokenId: BigNumber): Promise<void> {
+        const proxyAddress = (this._proxyContract as ERC721ProxyContract).address;
+        await this.approveAsync(proxyAddress, tokenAddress, tokenId);
+    }
+    public async approveProxyForAllAsync(tokenAddress: string, tokenId: BigNumber, isApproved: boolean): Promise<void> {
+        const tokenContract = this._getTokenContractFromAssetData(tokenAddress);
+        const tokenOwner = await this.ownerOfAsync(tokenAddress, tokenId);
+        const proxyAddress = (this._proxyContract as ERC721ProxyContract).address;
+        await this._web3Wrapper.awaitTransactionSuccessAsync(
+            await tokenContract.setApprovalForAll.sendTransactionAsync(proxyAddress, isApproved, {
+                from: tokenOwner,
+            }),
+            constants.AWAIT_TRANSACTION_MINED_MS,
+        );
+    }
+    public async approveAsync(to: string, tokenAddress: string, tokenId: BigNumber): Promise<void> {
+        const tokenContract = this._getTokenContractFromAssetData(tokenAddress);
+        const tokenOwner = await this.ownerOfAsync(tokenAddress, tokenId);
+        await this._web3Wrapper.awaitTransactionSuccessAsync(
+            await tokenContract.approve.sendTransactionAsync(to, tokenId, {
+                from: tokenOwner,
+            }),
+            constants.AWAIT_TRANSACTION_MINED_MS,
+        );
+    }
+    public async transferFromAsync(
+        tokenAddress: string,
+        tokenId: BigNumber,
+        currentOwner: string,
+        userAddress: string,
+    ): Promise<void> {
+        const tokenContract = this._getTokenContractFromAssetData(tokenAddress);
+        await this._web3Wrapper.awaitTransactionSuccessAsync(
+            await tokenContract.transferFrom.sendTransactionAsync(currentOwner, userAddress, tokenId, {
+                from: currentOwner,
+            }),
+            constants.AWAIT_TRANSACTION_MINED_MS,
+        );
+    }
+    public async mintAsync(tokenAddress: string, tokenId: BigNumber, userAddress: string): Promise<void> {
+        const tokenContract = this._getTokenContractFromAssetData(tokenAddress);
+        await this._web3Wrapper.awaitTransactionSuccessAsync(
+            await tokenContract.mint.sendTransactionAsync(userAddress, tokenId, {
+                from: this._contractOwnerAddress,
+            }),
+            constants.AWAIT_TRANSACTION_MINED_MS,
+        );
+    }
+    public async burnAsync(tokenAddress: string, tokenId: BigNumber, owner: string): Promise<void> {
+        const tokenContract = this._getTokenContractFromAssetData(tokenAddress);
+        await this._web3Wrapper.awaitTransactionSuccessAsync(
+            await tokenContract.burn.sendTransactionAsync(owner, tokenId, {
+                from: this._contractOwnerAddress,
+            }),
+            constants.AWAIT_TRANSACTION_MINED_MS,
+        );
+    }
+    public async ownerOfAsync(tokenAddress: string, tokenId: BigNumber): Promise<string> {
+        const tokenContract = this._getTokenContractFromAssetData(tokenAddress);
+        const owner = await tokenContract.ownerOf.callAsync(tokenId);
+        return owner;
+    }
+    public async isOwnerAsync(userAddress: string, tokenAddress: string, tokenId: BigNumber): Promise<boolean> {
+        const tokenContract = this._getTokenContractFromAssetData(tokenAddress);
+        const tokenOwner = await tokenContract.ownerOf.callAsync(tokenId);
+        const isOwner = tokenOwner === userAddress;
+        return isOwner;
+    }
+    public async isProxyApprovedForAllAsync(userAddress: string, tokenAddress: string): Promise<boolean> {
+        this._validateProxyContractExistsOrThrow();
+        const tokenContract = this._getTokenContractFromAssetData(tokenAddress);
+        const operator = (this._proxyContract as ERC721ProxyContract).address;
+        const didApproveAll = await tokenContract.isApprovedForAll.callAsync(userAddress, operator);
+        return didApproveAll;
+    }
+    public async isProxyApprovedAsync(tokenAddress: string, tokenId: BigNumber): Promise<boolean> {
+        this._validateProxyContractExistsOrThrow();
+        const tokenContract = this._getTokenContractFromAssetData(tokenAddress);
+        const approvedAddress = await tokenContract.getApproved.callAsync(tokenId);
+        const proxyAddress = (this._proxyContract as ERC721ProxyContract).address;
+        const isProxyAnApprovedOperator = approvedAddress === proxyAddress;
+        return isProxyAnApprovedOperator;
+    }
     public async getBalancesAsync(): Promise<ERC721TokenIdsByOwner> {
         this._validateDummyTokenContractsExistOrThrow();
         this._validateBalancesAndAllowancesSetOrThrow();
@@ -127,6 +209,13 @@ export class ERC721Wrapper {
         const tokenAddresses = _.map(this._dummyTokenContracts, dummyTokenContract => dummyTokenContract.address);
         return tokenAddresses;
     }
+    private _getTokenContractFromAssetData(tokenAddress: string): DummyERC721TokenContract {
+        const tokenContractIfExists = _.find(this._dummyTokenContracts, c => c.address === tokenAddress);
+        if (_.isUndefined(tokenContractIfExists)) {
+            throw new Error(`Token: ${tokenAddress} was not deployed through ERC20Wrapper`);
+        }
+        return tokenContractIfExists;
+    }
     private _validateDummyTokenContractsExistOrThrow(): void {
         if (_.isUndefined(this._dummyTokenContracts)) {
             throw new Error('Dummy ERC721 tokens not yet deployed, please call "deployDummyTokensAsync"');
diff --git a/packages/contracts/src/utils/exchange_wrapper.ts b/packages/contracts/src/utils/exchange_wrapper.ts
index 06eb70644..ad68c8ff4 100644
--- a/packages/contracts/src/utils/exchange_wrapper.ts
+++ b/packages/contracts/src/utils/exchange_wrapper.ts
@@ -33,8 +33,8 @@ export class ExchangeWrapper {
             params.signature,
             { from },
         );
-        const tx = await this._logDecoder.getTxWithDecodedLogsAsync(txHash);
-        return tx;
+        const txReceipt = await this._logDecoder.getTxWithDecodedLogsAsync(txHash);
+        return txReceipt;
     }
     public async cancelOrderAsync(signedOrder: SignedOrder, from: string): Promise<TransactionReceiptWithDecodedLogs> {
         const params = orderUtils.createCancel(signedOrder);
@@ -227,6 +227,10 @@ export class ExchangeWrapper {
         const filledAmount = new BigNumber(await this._exchange.filled.callAsync(orderHashHex));
         return filledAmount;
     }
+    public async isCancelledAsync(orderHashHex: string): Promise<boolean> {
+        const isCancelled = await this._exchange.cancelled.callAsync(orderHashHex);
+        return isCancelled;
+    }
     public async getOrderInfoAsync(signedOrder: SignedOrder): Promise<OrderInfo> {
         const orderInfo = (await this._exchange.getOrderInfo.callAsync(signedOrder)) as OrderInfo;
         return orderInfo;
diff --git a/packages/contracts/src/utils/order_factory_from_scenario.ts b/packages/contracts/src/utils/order_factory_from_scenario.ts
new file mode 100644
index 000000000..b150e59f6
--- /dev/null
+++ b/packages/contracts/src/utils/order_factory_from_scenario.ts
@@ -0,0 +1,277 @@
+import { assetProxyUtils, generatePseudoRandomSalt } from '@0xproject/order-utils';
+import { Order } from '@0xproject/types';
+import { BigNumber, errorUtils } from '@0xproject/utils';
+
+import { DummyERC721TokenContract } from '../generated_contract_wrappers/dummy_e_r_c721_token';
+
+import { constants } from './constants';
+import {
+    AssetDataScenario,
+    ERC721TokenIdsByOwner,
+    ExpirationTimeSecondsScenario,
+    FeeRecipientAddressScenario,
+    OrderAssetAmountScenario,
+    OrderScenario,
+    TakerScenario,
+} from './types';
+
+const TEN_UNITS_EIGHTEEN_DECIMALS = new BigNumber(10_000_000_000_000_000_000);
+const FIVE_UNITS_EIGHTEEN_DECIMALS = new BigNumber(5_000_000_000_000_000_000);
+const POINT_ONE_UNITS_EIGHTEEN_DECIMALS = new BigNumber(100_000_000_000_000_000);
+const POINT_ZERO_FIVE_UNITS_EIGHTEEN_DECIMALS = new BigNumber(50_000_000_000_000_000);
+const TEN_UNITS_FIVE_DECIMALS = new BigNumber(1_000_000);
+const FIVE_UNITS_FIVE_DECIMALS = new BigNumber(500_000);
+const ONE_NFT_UNIT = new BigNumber(1);
+
+export class OrderFactoryFromScenario {
+    private _userAddresses: string[];
+    private _zrxAddress: string;
+    private _nonZrxERC20EighteenDecimalTokenAddresses: string[];
+    private _erc20FiveDecimalTokenAddresses: string[];
+    private _erc721Token: DummyERC721TokenContract;
+    private _erc721Balances: ERC721TokenIdsByOwner;
+    private _exchangeAddress: string;
+    constructor(
+        userAddresses: string[],
+        zrxAddress: string,
+        nonZrxERC20EighteenDecimalTokenAddresses: string[],
+        erc20FiveDecimalTokenAddresses: string[],
+        erc721Token: DummyERC721TokenContract,
+        erc721Balances: ERC721TokenIdsByOwner,
+        exchangeAddress: string,
+    ) {
+        this._userAddresses = userAddresses;
+        this._zrxAddress = zrxAddress;
+        this._nonZrxERC20EighteenDecimalTokenAddresses = nonZrxERC20EighteenDecimalTokenAddresses;
+        this._erc20FiveDecimalTokenAddresses = erc20FiveDecimalTokenAddresses;
+        this._erc721Token = erc721Token;
+        this._erc721Balances = erc721Balances;
+        this._exchangeAddress = exchangeAddress;
+    }
+    public generateOrder(orderScenario: OrderScenario): Order {
+        const makerAddress = this._userAddresses[1];
+        let takerAddress = this._userAddresses[2];
+        const erc721MakerAssetIds = this._erc721Balances[makerAddress][this._erc721Token.address];
+        const erc721TakerAssetIds = this._erc721Balances[takerAddress][this._erc721Token.address];
+        let feeRecipientAddress;
+        let makerAssetAmount;
+        let takerAssetAmount;
+        let makerFee;
+        let takerFee;
+        let expirationTimeSeconds;
+        let makerAssetData;
+        let takerAssetData;
+
+        switch (orderScenario.feeRecipientScenario) {
+            case FeeRecipientAddressScenario.BurnAddress:
+                feeRecipientAddress = constants.NULL_ADDRESS;
+                break;
+            case FeeRecipientAddressScenario.EthUserAddress:
+                feeRecipientAddress = this._userAddresses[4];
+                break;
+            default:
+                throw errorUtils.spawnSwitchErr('FeeRecipientAddressScenario', orderScenario.feeRecipientScenario);
+        }
+
+        switch (orderScenario.makerAssetDataScenario) {
+            case AssetDataScenario.ZRXFeeToken:
+                makerAssetData = assetProxyUtils.encodeERC20AssetData(this._zrxAddress);
+                break;
+            case AssetDataScenario.ERC20NonZRXEighteenDecimals:
+                makerAssetData = assetProxyUtils.encodeERC20AssetData(
+                    this._nonZrxERC20EighteenDecimalTokenAddresses[0],
+                );
+                break;
+            case AssetDataScenario.ERC20FiveDecimals:
+                makerAssetData = assetProxyUtils.encodeERC20AssetData(this._erc20FiveDecimalTokenAddresses[0]);
+                break;
+            case AssetDataScenario.ERC721:
+                makerAssetData = assetProxyUtils.encodeERC721AssetData(
+                    this._erc721Token.address,
+                    erc721MakerAssetIds[0],
+                );
+                break;
+            default:
+                throw errorUtils.spawnSwitchErr('AssetDataScenario', orderScenario.makerAssetDataScenario);
+        }
+
+        switch (orderScenario.takerAssetDataScenario) {
+            case AssetDataScenario.ZRXFeeToken:
+                takerAssetData = assetProxyUtils.encodeERC20AssetData(this._zrxAddress);
+                break;
+            case AssetDataScenario.ERC20NonZRXEighteenDecimals:
+                takerAssetData = assetProxyUtils.encodeERC20AssetData(
+                    this._nonZrxERC20EighteenDecimalTokenAddresses[1],
+                );
+                break;
+            case AssetDataScenario.ERC20FiveDecimals:
+                takerAssetData = assetProxyUtils.encodeERC20AssetData(this._erc20FiveDecimalTokenAddresses[1]);
+                break;
+            case AssetDataScenario.ERC721:
+                takerAssetData = assetProxyUtils.encodeERC721AssetData(
+                    this._erc721Token.address,
+                    erc721TakerAssetIds[0],
+                );
+                break;
+            default:
+                throw errorUtils.spawnSwitchErr('AssetDataScenario', orderScenario.takerAssetDataScenario);
+        }
+
+        switch (orderScenario.makerAssetAmountScenario) {
+            case OrderAssetAmountScenario.Large:
+                switch (orderScenario.makerAssetDataScenario) {
+                    case AssetDataScenario.ZRXFeeToken:
+                    case AssetDataScenario.ERC20NonZRXEighteenDecimals:
+                        makerAssetAmount = TEN_UNITS_EIGHTEEN_DECIMALS;
+                        break;
+                    case AssetDataScenario.ERC20FiveDecimals:
+                        makerAssetAmount = TEN_UNITS_FIVE_DECIMALS;
+                        break;
+                    case AssetDataScenario.ERC721:
+                        makerAssetAmount = ONE_NFT_UNIT;
+                        break;
+                    default:
+                        throw errorUtils.spawnSwitchErr('AssetDataScenario', orderScenario.makerAssetDataScenario);
+                }
+                break;
+            case OrderAssetAmountScenario.Small:
+                switch (orderScenario.makerAssetDataScenario) {
+                    case AssetDataScenario.ZRXFeeToken:
+                    case AssetDataScenario.ERC20NonZRXEighteenDecimals:
+                        makerAssetAmount = FIVE_UNITS_EIGHTEEN_DECIMALS;
+                        break;
+                    case AssetDataScenario.ERC20FiveDecimals:
+                        makerAssetAmount = FIVE_UNITS_FIVE_DECIMALS;
+                        break;
+                    case AssetDataScenario.ERC721:
+                        makerAssetAmount = ONE_NFT_UNIT;
+                        break;
+                    default:
+                        throw errorUtils.spawnSwitchErr('AssetDataScenario', orderScenario.makerAssetDataScenario);
+                }
+                break;
+            case OrderAssetAmountScenario.Zero:
+                makerAssetAmount = new BigNumber(0);
+                break;
+            default:
+                throw errorUtils.spawnSwitchErr('OrderAssetAmountScenario', orderScenario.makerAssetAmountScenario);
+        }
+
+        switch (orderScenario.takerAssetAmountScenario) {
+            case OrderAssetAmountScenario.Large:
+                switch (orderScenario.takerAssetDataScenario) {
+                    case AssetDataScenario.ERC20NonZRXEighteenDecimals:
+                    case AssetDataScenario.ZRXFeeToken:
+                        takerAssetAmount = TEN_UNITS_EIGHTEEN_DECIMALS;
+                        break;
+                    case AssetDataScenario.ERC20FiveDecimals:
+                        takerAssetAmount = TEN_UNITS_FIVE_DECIMALS;
+                        break;
+                    case AssetDataScenario.ERC721:
+                        takerAssetAmount = ONE_NFT_UNIT;
+                        break;
+                    default:
+                        throw errorUtils.spawnSwitchErr('AssetDataScenario', orderScenario.takerAssetDataScenario);
+                }
+                break;
+            case OrderAssetAmountScenario.Small:
+                switch (orderScenario.takerAssetDataScenario) {
+                    case AssetDataScenario.ERC20NonZRXEighteenDecimals:
+                    case AssetDataScenario.ZRXFeeToken:
+                        takerAssetAmount = FIVE_UNITS_EIGHTEEN_DECIMALS;
+                        break;
+                    case AssetDataScenario.ERC20FiveDecimals:
+                        takerAssetAmount = FIVE_UNITS_FIVE_DECIMALS;
+                        break;
+                    case AssetDataScenario.ERC721:
+                        takerAssetAmount = ONE_NFT_UNIT;
+                        break;
+                    default:
+                        throw errorUtils.spawnSwitchErr('AssetDataScenario', orderScenario.takerAssetDataScenario);
+                }
+                break;
+            case OrderAssetAmountScenario.Zero:
+                takerAssetAmount = new BigNumber(0);
+                break;
+            default:
+                throw errorUtils.spawnSwitchErr('OrderAssetAmountScenario', orderScenario.takerAssetAmountScenario);
+        }
+
+        switch (orderScenario.makerFeeScenario) {
+            case OrderAssetAmountScenario.Large:
+                makerFee = POINT_ONE_UNITS_EIGHTEEN_DECIMALS;
+                break;
+            case OrderAssetAmountScenario.Small:
+                makerFee = POINT_ZERO_FIVE_UNITS_EIGHTEEN_DECIMALS;
+                break;
+            case OrderAssetAmountScenario.Zero:
+                makerFee = new BigNumber(0);
+                break;
+            default:
+                throw errorUtils.spawnSwitchErr('OrderAssetAmountScenario', orderScenario.makerFeeScenario);
+        }
+
+        switch (orderScenario.takerFeeScenario) {
+            case OrderAssetAmountScenario.Large:
+                takerFee = POINT_ONE_UNITS_EIGHTEEN_DECIMALS;
+                break;
+            case OrderAssetAmountScenario.Small:
+                takerFee = POINT_ZERO_FIVE_UNITS_EIGHTEEN_DECIMALS;
+                break;
+            case OrderAssetAmountScenario.Zero:
+                takerFee = new BigNumber(0);
+                break;
+            default:
+                throw errorUtils.spawnSwitchErr('OrderAssetAmountScenario', orderScenario.takerFeeScenario);
+        }
+
+        switch (orderScenario.expirationTimeSecondsScenario) {
+            case ExpirationTimeSecondsScenario.InFuture:
+                expirationTimeSeconds = new BigNumber(2524604400); // Close to infinite
+                break;
+            case ExpirationTimeSecondsScenario.InPast:
+                expirationTimeSeconds = new BigNumber(0); // Jan 1, 1970
+                break;
+            default:
+                throw errorUtils.spawnSwitchErr(
+                    'ExpirationTimeSecondsScenario',
+                    orderScenario.expirationTimeSecondsScenario,
+                );
+        }
+
+        switch (orderScenario.takerScenario) {
+            case TakerScenario.CorrectlySpecified:
+                break; // noop since takerAddress is already specified
+
+            case TakerScenario.IncorrectlySpecified:
+                const notTaker = this._userAddresses[3];
+                takerAddress = notTaker;
+                break;
+
+            case TakerScenario.Unspecified:
+                takerAddress = constants.NULL_ADDRESS;
+                break;
+
+            default:
+                throw errorUtils.spawnSwitchErr('TakerScenario', orderScenario.takerScenario);
+        }
+
+        const order = {
+            senderAddress: constants.NULL_ADDRESS,
+            makerAddress,
+            takerAddress,
+            makerFee,
+            takerFee,
+            makerAssetAmount,
+            takerAssetAmount,
+            makerAssetData,
+            takerAssetData,
+            salt: generatePseudoRandomSalt(),
+            exchangeAddress: this._exchangeAddress,
+            feeRecipientAddress,
+            expirationTimeSeconds,
+        };
+
+        return order;
+    }
+}
diff --git a/packages/contracts/src/utils/order_utils.ts b/packages/contracts/src/utils/order_utils.ts
index a9f994d80..019f6e74b 100644
--- a/packages/contracts/src/utils/order_utils.ts
+++ b/packages/contracts/src/utils/order_utils.ts
@@ -5,6 +5,13 @@ import { constants } from './constants';
 import { CancelOrder, MatchOrder } from './types';
 
 export const orderUtils = {
+    getPartialAmount(numerator: BigNumber, denominator: BigNumber, target: BigNumber): BigNumber {
+        const partialAmount = numerator
+            .mul(target)
+            .div(denominator)
+            .floor();
+        return partialAmount;
+    },
     createFill: (signedOrder: SignedOrder, takerAssetFillAmount?: BigNumber) => {
         const fill = {
             order: orderUtils.getOrderWithoutExchangeAddress(signedOrder),
diff --git a/packages/contracts/src/utils/simple_asset_balance_and_proxy_allowance_fetcher.ts b/packages/contracts/src/utils/simple_asset_balance_and_proxy_allowance_fetcher.ts
new file mode 100644
index 000000000..a295a40c4
--- /dev/null
+++ b/packages/contracts/src/utils/simple_asset_balance_and_proxy_allowance_fetcher.ts
@@ -0,0 +1,19 @@
+import { AbstractBalanceAndProxyAllowanceFetcher } from '@0xproject/order-utils';
+import { BigNumber } from '@0xproject/utils';
+
+import { AssetWrapper } from './asset_wrapper';
+
+export class SimpleAssetBalanceAndProxyAllowanceFetcher implements AbstractBalanceAndProxyAllowanceFetcher {
+    private _assetWrapper: AssetWrapper;
+    constructor(assetWrapper: AssetWrapper) {
+        this._assetWrapper = assetWrapper;
+    }
+    public async getBalanceAsync(assetData: string, userAddress: string): Promise<BigNumber> {
+        const balance = await this._assetWrapper.getBalanceAsync(userAddress, assetData);
+        return balance;
+    }
+    public async getProxyAllowanceAsync(assetData: string, userAddress: string): Promise<BigNumber> {
+        const proxyAllowance = await this._assetWrapper.getProxyAllowanceAsync(userAddress, assetData);
+        return proxyAllowance;
+    }
+}
diff --git a/packages/contracts/src/utils/simple_order_filled_cancelled_fetcher.ts b/packages/contracts/src/utils/simple_order_filled_cancelled_fetcher.ts
new file mode 100644
index 000000000..24afe36b7
--- /dev/null
+++ b/packages/contracts/src/utils/simple_order_filled_cancelled_fetcher.ts
@@ -0,0 +1,24 @@
+import { AbstractOrderFilledCancelledFetcher } from '@0xproject/order-utils';
+import { BigNumber } from '@0xproject/utils';
+
+import { ExchangeWrapper } from './exchange_wrapper';
+
+export class SimpleOrderFilledCancelledFetcher implements AbstractOrderFilledCancelledFetcher {
+    private _exchangeWrapper: ExchangeWrapper;
+    private _zrxAssetData: string;
+    constructor(exchange: ExchangeWrapper, zrxAssetData: string) {
+        this._exchangeWrapper = exchange;
+        this._zrxAssetData = zrxAssetData;
+    }
+    public async getFilledTakerAmountAsync(orderHash: string): Promise<BigNumber> {
+        const filledTakerAmount = new BigNumber(await this._exchangeWrapper.getTakerAssetFilledAmountAsync(orderHash));
+        return filledTakerAmount;
+    }
+    public async isOrderCancelledAsync(orderHash: string): Promise<boolean> {
+        const isCancelled = await this._exchangeWrapper.isCancelledAsync(orderHash);
+        return isCancelled;
+    }
+    public getZRXAssetData(): string {
+        return this._zrxAssetData;
+    }
+}
diff --git a/packages/contracts/src/utils/types.ts b/packages/contracts/src/utils/types.ts
index 5dfac64fc..b792bb90a 100644
--- a/packages/contracts/src/utils/types.ts
+++ b/packages/contracts/src/utils/types.ts
@@ -150,3 +150,80 @@ export interface MatchOrder {
     leftSignature: string;
     rightSignature: string;
 }
+
+// Combinatorial testing types
+
+export enum FeeRecipientAddressScenario {
+    BurnAddress = 'BURN_ADDRESS',
+    EthUserAddress = 'ETH_USER_ADDRESS',
+}
+
+export enum OrderAssetAmountScenario {
+    Zero = 'ZERO',
+    Large = 'LARGE',
+    Small = 'SMALL',
+}
+
+export enum TakerScenario {
+    CorrectlySpecified = 'CORRECTLY_SPECIFIED',
+    IncorrectlySpecified = 'INCORRECTLY_SPECIFIED',
+    Unspecified = 'UNSPECIFIED',
+}
+
+export enum ExpirationTimeSecondsScenario {
+    InPast = 'IN_PAST',
+    InFuture = 'IN_FUTURE',
+}
+
+export enum AssetDataScenario {
+    ERC721 = 'ERC721',
+    ZRXFeeToken = 'ZRX_FEE_TOKEN',
+    ERC20FiveDecimals = 'ERC20_FIVE_DECIMALS',
+    ERC20NonZRXEighteenDecimals = 'ERC20_NON_ZRX_EIGHTEEN_DECIMALS',
+}
+
+export enum TakerAssetFillAmountScenario {
+    Zero = 'ZERO',
+    GreaterThanRemainingFillableTakerAssetAmount = 'GREATER_THAN_REMAINING_FILLABLE_TAKER_ASSET_AMOUNT',
+    LessThanRemainingFillableTakerAssetAmount = 'LESS_THAN_REMAINING_FILLABLE_TAKER_ASSET_AMOUNT',
+    ExactlyRemainingFillableTakerAssetAmount = 'EXACTLY_REMAINING_FILLABLE_TAKER_ASSET_AMOUNT',
+}
+
+export interface OrderScenario {
+    takerScenario: TakerScenario;
+    feeRecipientScenario: FeeRecipientAddressScenario;
+    makerAssetAmountScenario: OrderAssetAmountScenario;
+    takerAssetAmountScenario: OrderAssetAmountScenario;
+    makerFeeScenario: OrderAssetAmountScenario;
+    takerFeeScenario: OrderAssetAmountScenario;
+    expirationTimeSecondsScenario: ExpirationTimeSecondsScenario;
+    makerAssetDataScenario: AssetDataScenario;
+    takerAssetDataScenario: AssetDataScenario;
+}
+
+export enum BalanceAmountScenario {
+    Exact = 'EXACT',
+    TooLow = 'TOO_LOW',
+    Higher = 'HIGHER',
+}
+
+export enum AllowanceAmountScenario {
+    Exact = 'EXACT',
+    TooLow = 'TOO_LOW',
+    Higher = 'HIGHER',
+    Unlimited = 'UNLIMITED',
+}
+
+export interface TraderStateScenario {
+    traderAssetBalance: BalanceAmountScenario;
+    traderAssetAllowance: AllowanceAmountScenario;
+    zrxFeeBalance: BalanceAmountScenario;
+    zrxFeeAllowance: AllowanceAmountScenario;
+}
+
+export interface FillScenario {
+    orderScenario: OrderScenario;
+    takerAssetFillAmountScenario: TakerAssetFillAmountScenario;
+    makerStateScenario: TraderStateScenario;
+    takerStateScenario: TraderStateScenario;
+}