fix(contracts): Catch cases where the actual error differs from the expected error (#1032)

* Catch cases where the actual error differs from the expected error

* Add tests for testWithReferenceFuncAsync

* Small style and comment fixes

1 files changed, 63 insertions, 0 deletions

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}',
+        );
+    });
+});