Merge branch 'development' into dev-dropdown

* development:
  fix(contracts): Catch cases where the actual error differs from the expected error (#1032)
  Add clarifying comments
  Remove redundant mstores from fillOrderNoThrow
  fix(contracts): Use correct error message for division by zero

5 files changed, 113 insertions, 37 deletions

diff --git a/packages/contracts/src/2.0.0/extensions/Forwarder/MixinExchangeWrapper.sol b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinExchangeWrapper.sol
index a7ff400b9..9e816716c 100644
--- a/packages/contracts/src/2.0.0/extensions/Forwarder/MixinExchangeWrapper.sol
+++ b/packages/contracts/src/2.0.0/extensions/Forwarder/MixinExchangeWrapper.sol
@@ -69,20 +69,14 @@ contract MixinExchangeWrapper is
                 fillOrderCalldata,                  // write output over input
                 128                                 // output size is 128 bytes
             )
-            switch success
-            case 0 {
-                mstore(fillResults, 0)
-                mstore(add(fillResults, 32), 0)
-                mstore(add(fillResults, 64), 0)
-                mstore(add(fillResults, 96), 0)
-            }
-            case 1 {
+            if success {
                 mstore(fillResults, mload(fillOrderCalldata))
                 mstore(add(fillResults, 32), mload(add(fillOrderCalldata, 32)))
                 mstore(add(fillResults, 64), mload(add(fillOrderCalldata, 64)))
                 mstore(add(fillResults, 96), mload(add(fillOrderCalldata, 96)))
             }
         }
+        // fillResults values will be 0 by default if call was unsuccessful
         return fillResults;
     }
 
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol b/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol
index 39fa724cc..a5459a21e 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol
@@ -96,6 +96,7 @@ contract MixinWrapperFunctions is
                 mstore(add(fillResults, 96), mload(add(fillOrderCalldata, 96)))
             }
         }
+        // fillResults values will be 0 by default if call was unsuccessful
         return fillResults;
     }
 
diff --git a/packages/contracts/test/exchange/internal.ts b/packages/contracts/test/exchange/internal.ts
index 2521665c2..de381fca3 100644
--- a/packages/contracts/test/exchange/internal.ts
+++ b/packages/contracts/test/exchange/internal.ts
@@ -67,9 +67,7 @@ describe('Exchange core internal functions', () => {
         overflowErrorForSendTransaction = new Error(
             await getRevertReasonOrErrorMessageForSendTransactionAsync(RevertReason.Uint256Overflow),
         );
-        divisionByZeroErrorForCall = new Error(
-            await getRevertReasonOrErrorMessageForSendTransactionAsync(RevertReason.DivisionByZero),
-        );
+        divisionByZeroErrorForCall = new Error(RevertReason.DivisionByZero);
         invalidOpcodeErrorForCall = new Error(await getInvalidOpcodeErrorMessageForCallAsync());
     });
     // Note(albrow): Don't forget to add beforeEach and afterEach calls to reset
diff --git a/packages/contracts/test/utils/test_with_reference.ts b/packages/contracts/test/utils/test_with_reference.ts
index 599b1eed4..b80be4a6c 100644
--- a/packages/contracts/test/utils/test_with_reference.ts
+++ b/packages/contracts/test/utils/test_with_reference.ts
@@ -6,6 +6,34 @@ import { chaiSetup } from './chai_setup';
 chaiSetup.configure();
 const expect = chai.expect;
 
+class Value<T> {
+    public value: T;
+    constructor(value: T) {
+        this.value = value;
+    }
+}
+
+// tslint:disable-next-line: max-classes-per-file
+class ErrorMessage {
+    public error: string;
+    constructor(message: string) {
+        this.error = message;
+    }
+}
+
+type PromiseResult<T> = Value<T> | ErrorMessage;
+
+// TODO(albrow): This seems like a generic utility function that could exist in
+// lodash. We should replace it by a library implementation, or move it to our
+// own.
+async function evaluatePromise<T>(promise: Promise<T>): Promise<PromiseResult<T>> {
+    try {
+        return new Value<T>(await promise);
+    } catch (e) {
+        return new ErrorMessage(e.message);
+    }
+}
+
 export async function testWithReferenceFuncAsync<P0, R>(
     referenceFunc: (p0: P0) => Promise<R>,
     testFunc: (p0: P0) => Promise<R>,
@@ -64,39 +92,31 @@ export async function testWithReferenceFuncAsync(
     testFuncAsync: (...args: any[]) => Promise<any>,
     values: any[],
 ): Promise<void> {
-    let expectedResult: any;
-    let expectedErr: string | undefined;
-    try {
-        expectedResult = await referenceFuncAsync(...values);
-    } catch (e) {
-        expectedErr = e.message;
-    }
-    let actualResult: any | undefined;
-    try {
-        actualResult = await testFuncAsync(...values);
-        if (!_.isUndefined(expectedErr)) {
+    // Measure correct behaviour
+    const expected = await evaluatePromise(referenceFuncAsync(...values));
+
+    // Measure actual behaviour
+    const actual = await evaluatePromise(testFuncAsync(...values));
+
+    // Compare behaviour
+    if (expected instanceof ErrorMessage) {
+        // If we expected an error, check if the actual error message contains the
+        // expected error message.
+        if (!(actual instanceof ErrorMessage)) {
             throw new Error(
-                `Expected error containing ${expectedErr} but got no error\n\tTest case: ${_getTestCaseString(
+                `Expected error containing ${expected.error} but got no error\n\tTest case: ${_getTestCaseString(
                     referenceFuncAsync,
                     values,
                 )}`,
             );
         }
-    } catch (e) {
-        if (_.isUndefined(expectedErr)) {
-            throw new Error(`${e.message}\n\tTest case: ${_getTestCaseString(referenceFuncAsync, values)}`);
-        } else {
-            expect(e.message).to.contain(
-                expectedErr,
-                `${e.message}\n\tTest case: ${_getTestCaseString(referenceFuncAsync, values)}`,
-            );
-        }
-    }
-    if (!_.isUndefined(actualResult) && !_.isUndefined(expectedResult)) {
-        expect(actualResult).to.deep.equal(
-            expectedResult,
-            `Test case: ${_getTestCaseString(referenceFuncAsync, values)}`,
+        expect(actual.error).to.contain(
+            expected.error,
+            `${actual.error}\n\tTest case: ${_getTestCaseString(referenceFuncAsync, values)}`,
         );
+    } else {
+        // If we do not expect an error, compare actual and expected directly.
+        expect(actual).to.deep.equal(expected, `Test case ${_getTestCaseString(referenceFuncAsync, values)}`);
     }
 }
 
diff --git a/packages/contracts/test/utils_test/test_with_reference.ts b/packages/contracts/test/utils_test/test_with_reference.ts
new file mode 100644
index 000000000..8d633cd1f
--- /dev/null
+++ b/packages/contracts/test/utils_test/test_with_reference.ts
@@ -0,0 +1,63 @@
+import * as chai from 'chai';
+
+import { chaiSetup } from '../utils/chai_setup';
+import { testWithReferenceFuncAsync } from '../utils/test_with_reference';
+
+chaiSetup.configure();
+const expect = chai.expect;
+
+async function divAsync(x: number, y: number): Promise<number> {
+    if (y === 0) {
+        throw new Error('MathError: divide by zero');
+    }
+    return x / y;
+}
+
+// returns an async function that always returns the given value.
+function alwaysValueFunc(value: number): (x: number, y: number) => Promise<number> {
+    return async (x: number, y: number) => value;
+}
+
+// returns an async function which always throws/rejects with the given error
+// message.
+function alwaysFailFunc(errMessage: string): (x: number, y: number) => Promise<number> {
+    return async (x: number, y: number) => {
+        throw new Error(errMessage);
+    };
+}
+
+describe('testWithReferenceFuncAsync', () => {
+    it('passes when both succeed and actual === expected', async () => {
+        await testWithReferenceFuncAsync(alwaysValueFunc(0.5), divAsync, [1, 2]);
+    });
+
+    it('passes when both fail and actual error contains expected error', async () => {
+        await testWithReferenceFuncAsync(alwaysFailFunc('divide by zero'), divAsync, [1, 0]);
+    });
+
+    it('fails when both succeed and actual !== expected', async () => {
+        expect(testWithReferenceFuncAsync(alwaysValueFunc(3), divAsync, [1, 2])).to.be.rejectedWith(
+            'Test case {"x":1,"y":2}: expected { value: 0.5 } to deeply equal { value: 3 }',
+        );
+    });
+
+    it('fails when both fail and actual error does not contain expected error', async () => {
+        expect(
+            testWithReferenceFuncAsync(alwaysFailFunc('Unexpected math error'), divAsync, [1, 0]),
+        ).to.be.rejectedWith(
+            'MathError: divide by zero\n\tTest case: {"x":1,"y":0}: expected \'MathError: divide by zero\' to include \'Unexpected math error\'',
+        );
+    });
+
+    it('fails when referenceFunc succeeds and testFunc fails', async () => {
+        expect(testWithReferenceFuncAsync(alwaysValueFunc(0), divAsync, [1, 0])).to.be.rejectedWith(
+            'Test case {"x":1,"y":0}: expected { error: \'MathError: divide by zero\' } to deeply equal { value: 0 }',
+        );
+    });
+
+    it('fails when referenceFunc fails and testFunc succeeds', async () => {
+        expect(testWithReferenceFuncAsync(alwaysFailFunc('divide by zero'), divAsync, [1, 2])).to.be.rejectedWith(
+            'Expected error containing divide by zero but got no error\n\tTest case: {"x":1,"y":2}',
+        );
+    });
+});