Add combinatorial tests for internal Exchange functions (#807)

* WIP add combinatorial tests for internal Exchange functions

* Change combinitorial testing strategy based on feedback

* Check value of filled[orderHash] in updateFilledState tests

* Add combinatorial tests for addFillResults

* Add combinatorial tests for getPartialAmount

* Implement generic `testWithReferenceFuncAsync`

* Implement generic `testCombinatoriallyWithReferenceFuncAsync`

* Add combinatorial tests for isRoundingError

* Add combinatorial tests for calculateFillResults

* Add support for Geth in internal contract tests

* Fix contract artifacts

* Change DECIMAL_PLACES to 78 and add a note.

* Document new functions in utils

* Optimize tests by only reseting state when needed

* Rename/move some files

* Print parameter names on failure in testWithReferenceFuncAsync

* Add to changelog for utils package

* Appease various linters

* Rename some more things related to FillOrderCombinatorialUtils

* Remove .only from test/exchange/internal.ts

* Remove old test for isRoundingError and getPartialAmount

* Appease linters again

* Remove old todos

* Fix typos, add comments, rename some things

* Re-add some LibMath tests

* Update contract internal tests to use new SafeMath revert reasons

* Apply PR feedback from Amir

* Apply PR feedback from Remco

* Re-add networks to ZRXToken artifact

* Remove duplicate Whitelist in compiler.json

3 files changed, 361 insertions, 116 deletions

diff --git a/packages/contracts/test/exchange/fill_order.ts b/packages/contracts/test/exchange/fill_order.ts
index 029bd66e2..1494fe093 100644
--- a/packages/contracts/test/exchange/fill_order.ts
+++ b/packages/contracts/test/exchange/fill_order.ts
@@ -2,7 +2,10 @@ import { BlockchainLifecycle } from '@0xproject/dev-utils';
 import * as _ from 'lodash';
 
 import { chaiSetup } from '../utils/chai_setup';
-import { CoreCombinatorialUtils, coreCombinatorialUtilsFactoryAsync } from '../utils/core_combinatorial_utils';
+import {
+    FillOrderCombinatorialUtils,
+    fillOrderCombinatorialUtilsFactoryAsync,
+} from '../utils/fill_order_combinatorial_utils';
 import {
     AllowanceAmountScenario,
     AssetDataScenario,
@@ -47,11 +50,11 @@ const defaultFillScenario = {
 };
 
 describe('FillOrder Tests', () => {
-    let coreCombinatorialUtils: CoreCombinatorialUtils;
+    let fillOrderCombinatorialUtils: FillOrderCombinatorialUtils;
 
     before(async () => {
         await blockchainLifecycle.startAsync();
-        coreCombinatorialUtils = await coreCombinatorialUtilsFactoryAsync(web3Wrapper, txDefaults);
+        fillOrderCombinatorialUtils = await fillOrderCombinatorialUtilsFactoryAsync(web3Wrapper, txDefaults);
     });
     after(async () => {
         await blockchainLifecycle.revertAsync();
@@ -67,19 +70,19 @@ describe('FillOrder Tests', () => {
             _.forEach(fillScenarios, fillScenario => {
                 const description = `Combinatorial OrderFill: ${JSON.stringify(fillScenario)}`;
                 it(description, async () => {
-                    await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+                    await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
                 });
             });
         };
 
-        const allFillScenarios = CoreCombinatorialUtils.generateFillOrderCombinations();
+        const allFillScenarios = FillOrderCombinatorialUtils.generateFillOrderCombinations();
         describe('Combinatorially generated fills orders', () => test(allFillScenarios));
 
         it('should transfer the correct amounts when makerAssetAmount === takerAssetAmount', async () => {
             const fillScenario = {
                 ...defaultFillScenario,
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
         it('should transfer the correct amounts when makerAssetAmount > takerAssetAmount', async () => {
             const fillScenario = {
@@ -89,7 +92,7 @@ describe('FillOrder Tests', () => {
                     takerAssetAmountScenario: OrderAssetAmountScenario.Small,
                 },
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
         it('should transfer the correct amounts when makerAssetAmount < takerAssetAmount', async () => {
             const fillScenario = {
@@ -99,7 +102,7 @@ describe('FillOrder Tests', () => {
                     makerAssetAmountScenario: OrderAssetAmountScenario.Small,
                 },
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
         it('should transfer the correct amounts when taker is specified and order is claimed by taker', async () => {
             const fillScenario = {
@@ -109,14 +112,14 @@ describe('FillOrder Tests', () => {
                     takerScenario: TakerScenario.CorrectlySpecified,
                 },
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
         it('should fill remaining value if takerAssetFillAmount > remaining takerAssetAmount', async () => {
             const fillScenario = {
                 ...defaultFillScenario,
                 takerAssetFillAmountScenario: TakerAssetFillAmountScenario.GreaterThanRemainingFillableTakerAssetAmount,
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
         it('should throw when taker is specified and order is claimed by other', async () => {
             const fillScenario = {
@@ -126,7 +129,7 @@ describe('FillOrder Tests', () => {
                     takerScenario: TakerScenario.IncorrectlySpecified,
                 },
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
 
         it('should throw if makerAssetAmount is 0', async () => {
@@ -138,7 +141,7 @@ describe('FillOrder Tests', () => {
                 },
                 takerAssetFillAmountScenario: TakerAssetFillAmountScenario.GreaterThanRemainingFillableTakerAssetAmount,
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
 
         it('should throw if takerAssetAmount is 0', async () => {
@@ -150,7 +153,7 @@ describe('FillOrder Tests', () => {
                 },
                 takerAssetFillAmountScenario: TakerAssetFillAmountScenario.GreaterThanRemainingFillableTakerAssetAmount,
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
 
         it('should throw if takerAssetFillAmount is 0', async () => {
@@ -158,7 +161,7 @@ describe('FillOrder Tests', () => {
                 ...defaultFillScenario,
                 takerAssetFillAmountScenario: TakerAssetFillAmountScenario.Zero,
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
 
         it('should throw if an order is expired', async () => {
@@ -169,7 +172,7 @@ describe('FillOrder Tests', () => {
                     expirationTimeSecondsScenario: ExpirationTimeSecondsScenario.InPast,
                 },
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
 
         it('should throw if maker erc20Balances are too low to fill order', async () => {
@@ -180,7 +183,7 @@ describe('FillOrder Tests', () => {
                     traderAssetBalance: BalanceAmountScenario.TooLow,
                 },
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
 
         it('should throw if taker erc20Balances are too low to fill order', async () => {
@@ -191,7 +194,7 @@ describe('FillOrder Tests', () => {
                     traderAssetBalance: BalanceAmountScenario.TooLow,
                 },
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
 
         it('should throw if maker allowances are too low to fill order', async () => {
@@ -202,7 +205,7 @@ describe('FillOrder Tests', () => {
                     traderAssetAllowance: AllowanceAmountScenario.TooLow,
                 },
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
 
         it('should throw if taker allowances are too low to fill order', async () => {
@@ -213,7 +216,7 @@ describe('FillOrder Tests', () => {
                     traderAssetAllowance: AllowanceAmountScenario.TooLow,
                 },
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
     });
 
@@ -228,7 +231,7 @@ describe('FillOrder Tests', () => {
                 },
                 takerAssetFillAmountScenario: TakerAssetFillAmountScenario.ExactlyRemainingFillableTakerAssetAmount,
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
 
         it('should successfully fill order when makerAsset is ERC721 and takerAsset is ERC20', async () => {
@@ -241,7 +244,7 @@ describe('FillOrder Tests', () => {
                 },
                 takerAssetFillAmountScenario: TakerAssetFillAmountScenario.ExactlyRemainingFillableTakerAssetAmount,
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario, true);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario, true);
         });
 
         it('should successfully fill order when makerAsset is ERC20 and takerAsset is ERC721', async () => {
@@ -254,7 +257,7 @@ describe('FillOrder Tests', () => {
                 },
                 takerAssetFillAmountScenario: TakerAssetFillAmountScenario.ExactlyRemainingFillableTakerAssetAmount,
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
 
         it('should successfully fill order when makerAsset is ERC721 and approveAll is set for it', async () => {
@@ -271,7 +274,7 @@ describe('FillOrder Tests', () => {
                     traderAssetAllowance: AllowanceAmountScenario.Unlimited,
                 },
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
 
         it('should successfully fill order when makerAsset and takerAsset are ERC721 and approveAll is set for them', async () => {
@@ -292,7 +295,7 @@ describe('FillOrder Tests', () => {
                     traderAssetAllowance: AllowanceAmountScenario.Unlimited,
                 },
             };
-            await coreCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
+            await fillOrderCombinatorialUtils.testFillOrderScenarioAsync(provider, fillScenario);
         });
     });
 });
diff --git a/packages/contracts/test/exchange/internal.ts b/packages/contracts/test/exchange/internal.ts
new file mode 100644
index 000000000..67d1d2d2c
--- /dev/null
+++ b/packages/contracts/test/exchange/internal.ts
@@ -0,0 +1,305 @@
+import { BlockchainLifecycle } from '@0xproject/dev-utils';
+import { Order, RevertReason, SignedOrder } from '@0xproject/types';
+import { BigNumber } from '@0xproject/utils';
+import * as _ from 'lodash';
+
+import { TestExchangeInternalsContract } from '../../generated_contract_wrappers/test_exchange_internals';
+import { artifacts } from '../utils/artifacts';
+import {
+    getInvalidOpcodeErrorMessageForCallAsync,
+    getRevertReasonOrErrorMessageForSendTransactionAsync,
+} from '../utils/assertions';
+import { chaiSetup } from '../utils/chai_setup';
+import { bytes32Values, testCombinatoriallyWithReferenceFuncAsync, uint256Values } from '../utils/combinatorial_utils';
+import { constants } from '../utils/constants';
+import { FillResults } from '../utils/types';
+import { provider, txDefaults, web3Wrapper } from '../utils/web3_wrapper';
+
+chaiSetup.configure();
+const blockchainLifecycle = new BlockchainLifecycle(web3Wrapper);
+
+const MAX_UINT256 = new BigNumber(2).pow(256).minus(1);
+
+const emptyOrder: Order = {
+    senderAddress: constants.NULL_ADDRESS,
+    makerAddress: constants.NULL_ADDRESS,
+    takerAddress: constants.NULL_ADDRESS,
+    makerFee: new BigNumber(0),
+    takerFee: new BigNumber(0),
+    makerAssetAmount: new BigNumber(0),
+    takerAssetAmount: new BigNumber(0),
+    makerAssetData: '0x',
+    takerAssetData: '0x',
+    salt: new BigNumber(0),
+    exchangeAddress: constants.NULL_ADDRESS,
+    feeRecipientAddress: constants.NULL_ADDRESS,
+    expirationTimeSeconds: new BigNumber(0),
+};
+
+const emptySignedOrder: SignedOrder = {
+    ...emptyOrder,
+    signature: '',
+};
+
+const overflowErrorForCall = new Error(RevertReason.Uint256Overflow);
+
+async function referenceGetPartialAmountAsync(
+    numerator: BigNumber,
+    denominator: BigNumber,
+    target: BigNumber,
+): Promise<BigNumber> {
+    const invalidOpcodeErrorForCall = new Error(await getInvalidOpcodeErrorMessageForCallAsync());
+    const product = numerator.mul(target);
+    if (product.greaterThan(MAX_UINT256)) {
+        throw overflowErrorForCall;
+    }
+    if (denominator.eq(0)) {
+        throw invalidOpcodeErrorForCall;
+    }
+    return product.dividedToIntegerBy(denominator);
+}
+
+describe('Exchange core internal functions', () => {
+    let testExchange: TestExchangeInternalsContract;
+    let invalidOpcodeErrorForCall: Error | undefined;
+    let overflowErrorForSendTransaction: Error | undefined;
+
+    before(async () => {
+        await blockchainLifecycle.startAsync();
+    });
+    after(async () => {
+        await blockchainLifecycle.revertAsync();
+    });
+    before(async () => {
+        testExchange = await TestExchangeInternalsContract.deployFrom0xArtifactAsync(
+            artifacts.TestExchangeInternals,
+            provider,
+            txDefaults,
+        );
+        overflowErrorForSendTransaction = new Error(
+            await getRevertReasonOrErrorMessageForSendTransactionAsync(RevertReason.Uint256Overflow),
+        );
+        invalidOpcodeErrorForCall = new Error(await getInvalidOpcodeErrorMessageForCallAsync());
+    });
+    // Note(albrow): Don't forget to add beforeEach and afterEach calls to reset
+    // the blockchain state for any tests which modify it!
+
+    describe('addFillResults', async () => {
+        function makeFillResults(value: BigNumber): FillResults {
+            return {
+                makerAssetFilledAmount: value,
+                takerAssetFilledAmount: value,
+                makerFeePaid: value,
+                takerFeePaid: value,
+            };
+        }
+        async function referenceAddFillResultsAsync(
+            totalValue: BigNumber,
+            singleValue: BigNumber,
+        ): Promise<FillResults> {
+            // Note(albrow): Here, each of totalFillResults and
+            // singleFillResults will consist of fields with the same values.
+            // This should be safe because none of the fields in a given
+            // FillResults are ever used together in a mathemetical operation.
+            // They are only used with the corresponding field from *the other*
+            // FillResults, which are different.
+            const totalFillResults = makeFillResults(totalValue);
+            const singleFillResults = makeFillResults(singleValue);
+            // HACK(albrow): _.mergeWith mutates the first argument! To
+            // workaround this we use _.cloneDeep.
+            return _.mergeWith(
+                _.cloneDeep(totalFillResults),
+                singleFillResults,
+                (totalVal: BigNumber, singleVal: BigNumber) => {
+                    const newTotal = totalVal.add(singleVal);
+                    if (newTotal.greaterThan(MAX_UINT256)) {
+                        throw overflowErrorForCall;
+                    }
+                    return newTotal;
+                },
+            );
+        }
+        async function testAddFillResultsAsync(totalValue: BigNumber, singleValue: BigNumber): Promise<FillResults> {
+            const totalFillResults = makeFillResults(totalValue);
+            const singleFillResults = makeFillResults(singleValue);
+            return testExchange.publicAddFillResults.callAsync(totalFillResults, singleFillResults);
+        }
+        await testCombinatoriallyWithReferenceFuncAsync(
+            'addFillResults',
+            referenceAddFillResultsAsync,
+            testAddFillResultsAsync,
+            [uint256Values, uint256Values],
+        );
+    });
+
+    describe('calculateFillResults', async () => {
+        function makeOrder(
+            makerAssetAmount: BigNumber,
+            takerAssetAmount: BigNumber,
+            makerFee: BigNumber,
+            takerFee: BigNumber,
+        ): Order {
+            return {
+                ...emptyOrder,
+                makerAssetAmount,
+                takerAssetAmount,
+                makerFee,
+                takerFee,
+            };
+        }
+        async function referenceCalculateFillResultsAsync(
+            orderTakerAssetAmount: BigNumber,
+            takerAssetFilledAmount: BigNumber,
+            otherAmount: BigNumber,
+        ): Promise<FillResults> {
+            // Note(albrow): Here we are re-using the same value (otherAmount)
+            // for order.makerAssetAmount, order.makerFee, and order.takerFee.
+            // This should be safe because they are never used with each other
+            // in any mathematical operation in either the reference TypeScript
+            // implementation or the Solidity implementation of
+            // calculateFillResults.
+            return {
+                makerAssetFilledAmount: await referenceGetPartialAmountAsync(
+                    takerAssetFilledAmount,
+                    orderTakerAssetAmount,
+                    otherAmount,
+                ),
+                takerAssetFilledAmount,
+                makerFeePaid: await referenceGetPartialAmountAsync(
+                    takerAssetFilledAmount,
+                    orderTakerAssetAmount,
+                    otherAmount,
+                ),
+                takerFeePaid: await referenceGetPartialAmountAsync(
+                    takerAssetFilledAmount,
+                    orderTakerAssetAmount,
+                    otherAmount,
+                ),
+            };
+        }
+        async function testCalculateFillResultsAsync(
+            orderTakerAssetAmount: BigNumber,
+            takerAssetFilledAmount: BigNumber,
+            otherAmount: BigNumber,
+        ): Promise<FillResults> {
+            const order = makeOrder(otherAmount, orderTakerAssetAmount, otherAmount, otherAmount);
+            return testExchange.publicCalculateFillResults.callAsync(order, takerAssetFilledAmount);
+        }
+        await testCombinatoriallyWithReferenceFuncAsync(
+            'calculateFillResults',
+            referenceCalculateFillResultsAsync,
+            testCalculateFillResultsAsync,
+            [uint256Values, uint256Values, uint256Values],
+        );
+    });
+
+    describe('getPartialAmount', async () => {
+        async function testGetPartialAmountAsync(
+            numerator: BigNumber,
+            denominator: BigNumber,
+            target: BigNumber,
+        ): Promise<BigNumber> {
+            return testExchange.publicGetPartialAmount.callAsync(numerator, denominator, target);
+        }
+        await testCombinatoriallyWithReferenceFuncAsync(
+            'getPartialAmount',
+            referenceGetPartialAmountAsync,
+            testGetPartialAmountAsync,
+            [uint256Values, uint256Values, uint256Values],
+        );
+    });
+
+    describe('isRoundingError', async () => {
+        async function referenceIsRoundingErrorAsync(
+            numerator: BigNumber,
+            denominator: BigNumber,
+            target: BigNumber,
+        ): Promise<boolean> {
+            const product = numerator.mul(target);
+            if (denominator.eq(0)) {
+                throw invalidOpcodeErrorForCall;
+            }
+            const remainder = product.mod(denominator);
+            if (remainder.eq(0)) {
+                return false;
+            }
+            if (product.greaterThan(MAX_UINT256)) {
+                throw overflowErrorForCall;
+            }
+            if (product.eq(0)) {
+                throw invalidOpcodeErrorForCall;
+            }
+            const remainderTimes1000000 = remainder.mul('1000000');
+            if (remainderTimes1000000.greaterThan(MAX_UINT256)) {
+                throw overflowErrorForCall;
+            }
+            const errPercentageTimes1000000 = remainderTimes1000000.dividedToIntegerBy(product);
+            return errPercentageTimes1000000.greaterThan('1000');
+        }
+        async function testIsRoundingErrorAsync(
+            numerator: BigNumber,
+            denominator: BigNumber,
+            target: BigNumber,
+        ): Promise<boolean> {
+            return testExchange.publicIsRoundingError.callAsync(numerator, denominator, target);
+        }
+        await testCombinatoriallyWithReferenceFuncAsync(
+            'isRoundingError',
+            referenceIsRoundingErrorAsync,
+            testIsRoundingErrorAsync,
+            [uint256Values, uint256Values, uint256Values],
+        );
+    });
+
+    describe('updateFilledState', async () => {
+        // Note(albrow): Since updateFilledState modifies the state by calling
+        // sendTransaction, we must reset the state after each test.
+        beforeEach(async () => {
+            await blockchainLifecycle.startAsync();
+        });
+        afterEach(async () => {
+            await blockchainLifecycle.revertAsync();
+        });
+        async function referenceUpdateFilledStateAsync(
+            takerAssetFilledAmount: BigNumber,
+            orderTakerAssetFilledAmount: BigNumber,
+            // tslint:disable-next-line:no-unused-variable
+            orderHash: string,
+        ): Promise<BigNumber> {
+            const totalFilledAmount = takerAssetFilledAmount.add(orderTakerAssetFilledAmount);
+            if (totalFilledAmount.greaterThan(MAX_UINT256)) {
+                throw overflowErrorForSendTransaction;
+            }
+            return totalFilledAmount;
+        }
+        async function testUpdateFilledStateAsync(
+            takerAssetFilledAmount: BigNumber,
+            orderTakerAssetFilledAmount: BigNumber,
+            orderHash: string,
+        ): Promise<BigNumber> {
+            const fillResults = {
+                makerAssetFilledAmount: new BigNumber(0),
+                takerAssetFilledAmount,
+                makerFeePaid: new BigNumber(0),
+                takerFeePaid: new BigNumber(0),
+            };
+            await web3Wrapper.awaitTransactionSuccessAsync(
+                await testExchange.publicUpdateFilledState.sendTransactionAsync(
+                    emptySignedOrder,
+                    constants.NULL_ADDRESS,
+                    orderHash,
+                    orderTakerAssetFilledAmount,
+                    fillResults,
+                ),
+                constants.AWAIT_TRANSACTION_MINED_MS,
+            );
+            return testExchange.filled.callAsync(orderHash);
+        }
+        await testCombinatoriallyWithReferenceFuncAsync(
+            'updateFilledState',
+            referenceUpdateFilledStateAsync,
+            testUpdateFilledStateAsync,
+            [uint256Values, uint256Values, bytes32Values],
+        );
+    });
+});
diff --git a/packages/contracts/test/exchange/libs.ts b/packages/contracts/test/exchange/libs.ts
index 51794d8a3..5c9f9aac7 100644
--- a/packages/contracts/test/exchange/libs.ts
+++ b/packages/contracts/test/exchange/libs.ts
@@ -67,6 +67,35 @@ describe('Exchange libs', () => {
             });
         });
     });
+    // Note(albrow): These tests are designed to be supplemental to the
+    // combinatorial tests in test/exchange/internal. They test specific edge
+    // cases that are not covered by the combinatorial tests.
+    describe('LibMath', () => {
+        it('should return false if there is a rounding error of 0.1%', async () => {
+            const numerator = new BigNumber(20);
+            const denominator = new BigNumber(999);
+            const target = new BigNumber(50);
+            // rounding error = ((20*50/999) - floor(20*50/999)) / (20*50/999) = 0.1%
+            const isRoundingError = await libs.publicIsRoundingError.callAsync(numerator, denominator, target);
+            expect(isRoundingError).to.be.false();
+        });
+        it('should return false if there is a rounding of 0.09%', async () => {
+            const numerator = new BigNumber(20);
+            const denominator = new BigNumber(9991);
+            const target = new BigNumber(500);
+            // rounding error = ((20*500/9991) - floor(20*500/9991)) / (20*500/9991) = 0.09%
+            const isRoundingError = await libs.publicIsRoundingError.callAsync(numerator, denominator, target);
+            expect(isRoundingError).to.be.false();
+        });
+        it('should return true if there is a rounding error of 0.11%', async () => {
+            const numerator = new BigNumber(20);
+            const denominator = new BigNumber(9989);
+            const target = new BigNumber(500);
+            // rounding error = ((20*500/9989) - floor(20*500/9989)) / (20*500/9989) = 0.011%
+            const isRoundingError = await libs.publicIsRoundingError.callAsync(numerator, denominator, target);
+            expect(isRoundingError).to.be.true();
+        });
+    });
 
     describe('LibOrder', () => {
         describe('getOrderSchema', () => {
@@ -93,96 +122,4 @@ describe('Exchange libs', () => {
             });
         });
     });
-
-    describe('LibMath', () => {
-        describe('isRoundingError', () => {
-            it('should return false if there is a rounding error of 0.1%', async () => {
-                const numerator = new BigNumber(20);
-                const denominator = new BigNumber(999);
-                const target = new BigNumber(50);
-                // rounding error = ((20*50/999) - floor(20*50/999)) / (20*50/999) = 0.1%
-                const isRoundingError = await libs.publicIsRoundingError.callAsync(numerator, denominator, target);
-                expect(isRoundingError).to.be.false();
-            });
-
-            it('should return false if there is a rounding of 0.09%', async () => {
-                const numerator = new BigNumber(20);
-                const denominator = new BigNumber(9991);
-                const target = new BigNumber(500);
-                // rounding error = ((20*500/9991) - floor(20*500/9991)) / (20*500/9991) = 0.09%
-                const isRoundingError = await libs.publicIsRoundingError.callAsync(numerator, denominator, target);
-                expect(isRoundingError).to.be.false();
-            });
-
-            it('should return true if there is a rounding error of 0.11%', async () => {
-                const numerator = new BigNumber(20);
-                const denominator = new BigNumber(9989);
-                const target = new BigNumber(500);
-                // rounding error = ((20*500/9989) - floor(20*500/9989)) / (20*500/9989) = 0.011%
-                const isRoundingError = await libs.publicIsRoundingError.callAsync(numerator, denominator, target);
-                expect(isRoundingError).to.be.true();
-            });
-
-            it('should return true if there is a rounding error > 0.1%', async () => {
-                const numerator = new BigNumber(3);
-                const denominator = new BigNumber(7);
-                const target = new BigNumber(10);
-                // rounding error = ((3*10/7) - floor(3*10/7)) / (3*10/7) = 6.67%
-                const isRoundingError = await libs.publicIsRoundingError.callAsync(numerator, denominator, target);
-                expect(isRoundingError).to.be.true();
-            });
-
-            it('should return false when there is no rounding error', async () => {
-                const numerator = new BigNumber(1);
-                const denominator = new BigNumber(2);
-                const target = new BigNumber(10);
-
-                const isRoundingError = await libs.publicIsRoundingError.callAsync(numerator, denominator, target);
-                expect(isRoundingError).to.be.false();
-            });
-
-            it('should return false when there is rounding error <= 0.1%', async () => {
-                // randomly generated numbers
-                const numerator = new BigNumber(76564);
-                const denominator = new BigNumber(676373677);
-                const target = new BigNumber(105762562);
-                // rounding error = ((76564*105762562/676373677) - floor(76564*105762562/676373677)) /
-                // (76564*105762562/676373677) = 0.0007%
-                const isRoundingError = await libs.publicIsRoundingError.callAsync(numerator, denominator, target);
-                expect(isRoundingError).to.be.false();
-            });
-        });
-
-        describe('getPartialAmount', () => {
-            it('should return the numerator/denominator*target', async () => {
-                const numerator = new BigNumber(1);
-                const denominator = new BigNumber(2);
-                const target = new BigNumber(10);
-
-                const partialAmount = await libs.publicGetPartialAmount.callAsync(numerator, denominator, target);
-                const expectedPartialAmount = 5;
-                expect(partialAmount).to.be.bignumber.equal(expectedPartialAmount);
-            });
-
-            it('should round down', async () => {
-                const numerator = new BigNumber(2);
-                const denominator = new BigNumber(3);
-                const target = new BigNumber(10);
-
-                const partialAmount = await libs.publicGetPartialAmount.callAsync(numerator, denominator, target);
-                const expectedPartialAmount = 6;
-                expect(partialAmount).to.be.bignumber.equal(expectedPartialAmount);
-            });
-
-            it('should round .5 down', async () => {
-                const numerator = new BigNumber(1);
-                const denominator = new BigNumber(20);
-                const target = new BigNumber(10);
-
-                const partialAmount = await libs.publicGetPartialAmount.callAsync(numerator, denominator, target);
-                const expectedPartialAmount = 0;
-                expect(partialAmount).to.be.bignumber.equal(expectedPartialAmount);
-            });
-        });
-    });
 });