Mock timestamp

CHANGELOG.md

@@ -23,6 +23,7 @@
 * `[jest-environment-jsdom]` Fix asynchronous test will fail due to timeout issue. ([#4669](https://github.com/facebook/jest/pull/4669))
 
 ### Features
+* `[jest-mock]` Add `timestamps` to mock state. ([#4866](https://github.com/facebook/jest/pull/4866))
 * `[eslint-plugin-jest]` Add `prefer-to-have-length` lint rule. ([#4771](https://github.com/facebook/jest/pull/4771))
 * `[jest-environment-jsdom]` [**BREAKING**] Upgrade to JSDOM@11 ([#4770](https://github.com/facebook/jest/pull/4770))
 * `[jest-environment-*]` [**BREAKING**] Add Async Test Environment APIs, dispose is now teardown ([#4506](https://github.com/facebook/jest/pull/4506))

packages/jest-mock/README.md

@@ -80,11 +80,12 @@ the following members:
 
 ##### `.mock`
 
-An object with two members, `calls`, and `instances`, which are both
-lists. The items in the `calls` list are the arguments with which the
+An object with three members, `calls`, `instances` and `timestamps`, which are
+all lists. The items in the `calls` list are the arguments with which the
 function was called. The "instances" list stores the value of 'this' for
 each call to the function. This is useful for retrieving instances from a
-constructor.
+constructor. The `timestamps` list stores a number timestamp every time the
+mock is called.
 
 ##### `.mockReturnValueOnce(value)`
 

packages/jest-mock/src/__tests__/jest_mock.test.js

@@ -390,6 +390,72 @@ describe('moduleMocker', () => {
       expect(fake(2)).toEqual(42);
       expect(fake(2)).toEqual(4);
     });
+
+    describe('timestamps', () => {
+      const RealDate = Date;
+
+      beforeEach(() => {
+        global.Date = {
+          now: jest
+            .fn()
+            .mockImplementationOnce(() => 978391040765)
+            .mockImplementationOnce(() => 1262388620765),
+        };
+      });
+
+      afterEach(() => {
+        global.Date = RealDate;
+      });
+
+      it('tracks timestamps made by mocks', () => {
+        const fn = moduleMocker.fn();
+        expect(fn.mock.timestamps).toEqual([]);
+
+        fn(1, 2, 3);
+        expect(fn.mock.timestamps[0]).toBe(978391040765);
+
+        fn('a', 'b', 'c');
+        expect(fn.mock.timestamps[1]).toBe(1262388620765);
+      });
+
+      it('supports clearing mock timestamps', () => {
+        const fn = moduleMocker.fn();
+        expect(fn.mock.timestamps).toEqual([]);
+
+        fn(1, 2, 3);
+        expect(fn.mock.timestamps).toEqual([978391040765]);
+
+        fn.mockReturnValue('abcd');
+
+        fn.mockClear();
+        expect(fn.mock.timestamps).toEqual([]);
+
+        fn('a', 'b', 'c');
+        expect(fn.mock.timestamps).toEqual([1262388620765]);
+
+        expect(fn()).toEqual('abcd');
+      });
+
+      it('supports clearing all mocks timestamps', () => {
+        const fn1 = moduleMocker.fn();
+        fn1.mockImplementation(() => 'abcd');
+
+        fn1(1, 2, 3);
+        expect(fn1.mock.timestamps).toEqual([978391040765]);
+
+        const fn2 = moduleMocker.fn();
+
+        fn2.mockReturnValue('abcde');
+        fn2('a', 'b', 'c', 'd');
+        expect(fn2.mock.timestamps).toEqual([1262388620765]);
+
+        moduleMocker.clearAllMocks();
+        expect(fn1.mock.timestamps).toEqual([]);
+        expect(fn2.mock.timestamps).toEqual([]);
+        expect(fn1()).toEqual('abcd');
+        expect(fn2()).toEqual('abcde');
+      });
+    });
   });
 
   describe('getMockImplementation', () => {

packages/jest-mock/src/index.js

@@ -24,6 +24,7 @@ export type MockFunctionMetadata = {
 type MockFunctionState = {
   instances: Array<any>,
   calls: Array<Array<any>>,
+  timestamps: Array<number>,
 };
 
 type MockFunctionConfig = {
@@ -279,6 +280,7 @@ class ModuleMockerClass {
     return {
       calls: [],
       instances: [],
+      timestamps: [],
     };
   }
 
@@ -313,6 +315,7 @@ class ModuleMockerClass {
         const mockConfig = mocker._ensureMockConfig(f);
         mockState.instances.push(this);
         mockState.calls.push(Array.prototype.slice.call(arguments));
+        mockState.timestamps.push(Date.now());
         if (this instanceof f) {
           // This is probably being called as a constructor
           prototypeSlots.forEach(slot => {