1 files changed, 139 insertions, 0 deletions
diff --git a/contracts/core/test/utils/test_with_reference.ts b/contracts/core/test/utils/test_with_reference.ts
new file mode 100644
index 000000000..b80be4a6c
--- /dev/null
+++ b/contracts/core/test/utils/test_with_reference.ts
@@ -0,0 +1,139 @@
+import * as chai from 'chai';
+import * as _ from 'lodash';
+
+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>,
+    values: [P0],
+): Promise<void>;
+export async function testWithReferenceFuncAsync<P0, P1, R>(
+    referenceFunc: (p0: P0, p1: P1) => Promise<R>,
+    testFunc: (p0: P0, p1: P1) => Promise<R>,
+    values: [P0, P1],
+): Promise<void>;
+export async function testWithReferenceFuncAsync<P0, P1, P2, R>(
+    referenceFunc: (p0: P0, p1: P1, p2: P2) => Promise<R>,
+    testFunc: (p0: P0, p1: P1, p2: P2) => Promise<R>,
+    values: [P0, P1, P2],
+): Promise<void>;
+export async function testWithReferenceFuncAsync<P0, P1, P2, P3, R>(
+    referenceFunc: (p0: P0, p1: P1, p2: P2, p3: P3) => Promise<R>,
+    testFunc: (p0: P0, p1: P1, p2: P2, p3: P3) => Promise<R>,
+    values: [P0, P1, P2, P3],
+): Promise<void>;
+export async function testWithReferenceFuncAsync<P0, P1, P2, P3, P4, R>(
+    referenceFunc: (p0: P0, p1: P1, p2: P2, p3: P3, p4: P4) => Promise<R>,
+    testFunc: (p0: P0, p1: P1, p2: P2, p3: P3, p4: P4) => Promise<R>,
+    values: [P0, P1, P2, P3, P4],
+): Promise<void>;
+
+/**
+ * Tests the behavior of a test function by comparing it to the expected
+ * behavior (defined by a reference function).
+ *
+ * First the reference function will be called to obtain an "expected result",
+ * or if the reference function throws/rejects, an "expected error". Next, the
+ * test function will be called to obtain an "actual result", or if the test
+ * function throws/rejects, an "actual error". The test passes if at least one
+ * of the following conditions is met:
+ *
+ * 1) Neither the reference function or the test function throw and the
+ * "expected result" equals the "actual result".
+ *
+ * 2) Both the reference function and the test function throw and the "actual
+ * error" message *contains* the "expected error" message.
+ *
+ * @param referenceFuncAsync a reference function implemented in pure
+ * JavaScript/TypeScript which accepts N arguments and returns the "expected
+ * result" or throws/rejects with the "expected error".
+ * @param testFuncAsync a test function which, e.g., makes a call or sends a
+ * transaction to a contract. It accepts the same N arguments returns the
+ * "actual result" or throws/rejects with the "actual error".
+ * @param values an array of N values, where each value corresponds in-order to
+ * an argument to both the test function and the reference function.
+ * @return A Promise that resolves if the test passes and rejects if the test
+ * fails, according to the rules described above.
+ */
+export async function testWithReferenceFuncAsync(
+    referenceFuncAsync: (...args: any[]) => Promise<any>,
+    testFuncAsync: (...args: any[]) => Promise<any>,
+    values: any[],
+): Promise<void> {
+    // 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 ${expected.error} but got no error\n\tTest 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 ${_getTestCaseString(referenceFuncAsync, values)}`);
+    }
+}
+
+function _getTestCaseString(referenceFuncAsync: (...args: any[]) => Promise<any>, values: any[]): string {
+    const paramNames = _getParameterNames(referenceFuncAsync);
+    return JSON.stringify(_.zipObject(paramNames, values));
+}
+
+// Source: https://stackoverflow.com/questions/1007981/how-to-get-function-parameter-names-values-dynamically
+function _getParameterNames(func: (...args: any[]) => any): string[] {
+    return _.toString(func)
+        .replace(/[/][/].*$/gm, '') // strip single-line comments
+        .replace(/\s+/g, '') // strip white space
+        .replace(/[/][*][^/*]*[*][/]/g, '') // strip multi-line comments
+        .split('){', 1)[0]
+        .replace(/^[^(]*[(]/, '') // extract the parameters
+        .replace(/=[^,]+/g, '') // strip any ES6 defaults
+        .split(',')
+        .filter(Boolean); // split & filter [""]
+}