feat(jest-util): use lolex as implementation for fake timers

CHANGELOG.md

@@ -186,6 +186,7 @@ We skipped 24.2.0 because a draft was accidentally published. Please use `24.3.0
 - `[jest-jasmine2]` Will now only execute at most 5 concurrent tests _within the same testsuite_ when using `test.concurrent` ([#7770](https://github.com/facebook/jest/pull/7770))
 - `[jest-circus]` Same as `[jest-jasmine2]`, only 5 tests will run concurrently by default ([#7770](https://github.com/facebook/jest/pull/7770))
 - `[jest-config]` A new `maxConcurrency` option allows to change the number of tests allowed to run concurrently ([#7770](https://github.com/facebook/jest/pull/7770))
+- `[jest-util]`[**BREAKING**] Replace Jest's fake timers implementation with Lolex ([#5171](https://github.com/facebook/jest/pull/5171))
 
 ### Fixes
 

docs/JestObjectAPI.md

@@ -527,10 +527,6 @@ When this API is called, all pending macro-tasks and micro-tasks will be execute
 
 This is often useful for synchronously executing setTimeouts during a test in order to synchronously assert about some behavior that would only happen after the `setTimeout()` or `setInterval()` callbacks executed. See the [Timer mocks](TimerMocks.md) doc for more information.
 
-### `jest.runAllImmediates()`
-
-Exhausts all tasks queued by `setImmediate()`.
-
 ### `jest.advanceTimersByTime(msToRun)`
 
 ##### renamed in Jest **22.0.0+**
@@ -557,6 +553,14 @@ This means, if any timers have been scheduled (but have not yet executed), they
 
 Returns the number of fake timers still left to run.
 
+### `.jest.setSystemTime()`
+
+Set the current system time used by fake timers. Simulates a user changing the system clock while your program is running. It affects the current time but it does not in itself cause e.g. timers to fire; they will fire exactly as they would have done without the call to `jest.setSystemTime()`.
+
+### `.jest.getRealSystemTime()`
+
+When mocking time, `Date.now()` will also be mocked. If you for some reason need access to the real current time, you can invoke this function.
+
 ## Misc
 
 ### `jest.setTimeout(timeout)`

e2e/__tests__/fakePromises.test.ts

@@ -8,13 +8,8 @@
 import runJest from '../runJest';
 
 describe('Fake promises', () => {
-  it('should be possible to resolve with fake timers using immediates', () => {
-    const result = runJest('fake-promises/immediate');
-    expect(result.status).toBe(0);
-  });
-
-  it('should be possible to resolve with fake timers using asap', () => {
-    const result = runJest('fake-promises/asap');
+  it('should be possible to resolve with fake timers', () => {
+    const result = runJest('fake-promises');
     expect(result.status).toBe(0);
   });
 });

e2e/timer-reset-mocks/after-reset-all-mocks/timerAndMock.test.js

@@ -4,17 +4,17 @@ describe('timers', () => {
   it('should work before calling resetAllMocks', () => {
     jest.useFakeTimers();
     const f = jest.fn();
-    setImmediate(() => f());
-    jest.runAllImmediates();
-    expect(f.mock.calls.length).toBe(1);
+    setTimeout(f, 0);
+    jest.runAllTimers();
+    expect(f).toHaveBeenCalledTimes(1);
   });
 
   it('should not break after calling resetAllMocks', () => {
     jest.resetAllMocks();
     jest.useFakeTimers();
     const f = jest.fn();
-    setImmediate(() => f());
-    jest.runAllImmediates();
-    expect(f.mock.calls.length).toBe(1);
+    setTimeout(f, 0);
+    jest.runAllTimers();
+    expect(f).toHaveBeenCalledTimes(1);
   });
 });

e2e/timer-reset-mocks/with-reset-mocks/timerWithMock.test.js

@@ -4,8 +4,8 @@ describe('timers', () => {
   it('should work before calling resetAllMocks', () => {
     const f = jest.fn();
     jest.useFakeTimers();
-    setImmediate(() => f());
-    jest.runAllImmediates();
-    expect(f.mock.calls.length).toBe(1);
+    setTimeout(f, 0);
+    jest.runAllTimers();
+    expect(f).toHaveBeenCalledTimes(1);
   });
 });

examples/timer/__tests__/infinite_timer_game.test.js

@@ -5,15 +5,16 @@
 jest.useFakeTimers();
 
 it('schedules a 10-second timer after 1 second', () => {
+  jest.spyOn(global, 'setTimeout');
   const infiniteTimerGame = require('../infiniteTimerGame');
   const callback = jest.fn();
 
   infiniteTimerGame(callback);
 
   // At this point in time, there should have been a single call to
   // setTimeout to schedule the end of the game in 1 second.
-  expect(setTimeout.mock.calls.length).toBe(1);
-  expect(setTimeout.mock.calls[0][1]).toBe(1000);
+  expect(setTimeout).toBeCalledTimes(1);
+  expect(setTimeout).toHaveBeenNthCalledWith(1, expect.any(Function), 1000);
 
   // Fast forward and exhaust only currently pending timers
   // (but not any new timers that get created during that process)
@@ -24,6 +25,6 @@ it('schedules a 10-second timer after 1 second', () => {
 
   // And it should have created a new timer to start the game over in
   // 10 seconds
-  expect(setTimeout.mock.calls.length).toBe(2);
-  expect(setTimeout.mock.calls[1][1]).toBe(10000);
+  expect(setTimeout).toBeCalledTimes(2);
+  expect(setTimeout).toHaveBeenNthCalledWith(2, expect.any(Function), 10000);
 });

examples/timer/__tests__/timer_game.test.js

@@ -5,12 +5,15 @@
 jest.useFakeTimers();
 
 describe('timerGame', () => {
+  beforeEach(() => {
+    jest.spyOn(global, 'setTimeout');
+  });
   it('waits 1 second before ending the game', () => {
     const timerGame = require('../timerGame');
     timerGame();
 
-    expect(setTimeout.mock.calls.length).toBe(1);
-    expect(setTimeout.mock.calls[0][1]).toBe(1000);
+    expect(setTimeout).toBeCalledTimes(1);
+    expect(setTimeout).toBeCalledWith(expect.any(Function), 1000);
   });
 
   it('calls the callback after 1 second via runAllTimers', () => {
@@ -27,7 +30,7 @@ describe('timerGame', () => {
 
     // Now our callback should have been called!
     expect(callback).toBeCalled();
-    expect(callback.mock.calls.length).toBe(1);
+    expect(callback).toBeCalledTimes(1);
   });
 
   it('calls the callback after 1 second via advanceTimersByTime', () => {
@@ -44,6 +47,6 @@ describe('timerGame', () => {
 
     // Now our callback should have been called!
     expect(callback).toBeCalled();
-    expect(callback.mock.calls.length).toBe(1);
+    expect(callback).toBeCalledTimes(1);
   });
 });

packages/jest-environment-jsdom/src/index.ts

@@ -30,7 +30,7 @@ function isWin(globals: Win | Global.Global): globals is Win {
 
 class JSDOMEnvironment implements JestEnvironment {
   dom: JSDOM | null;
-  fakeTimers: FakeTimers<number> | null;
+  fakeTimers: FakeTimers | null;
   // @ts-ignore
   global: Global.Global | Win | null;
   errorEventListener: ((event: Event & {error: Error}) => void) | null;
@@ -87,17 +87,7 @@ class JSDOMEnvironment implements JestEnvironment {
 
     this.moduleMocker = new mock.ModuleMocker(global as any);
 
-    const timerConfig = {
-      idToRef: (id: number) => id,
-      refToId: (ref: number) => ref,
-    };
-
-    this.fakeTimers = new FakeTimers({
-      config,
-      global: global as any,
-      moduleMocker: this.moduleMocker,
-      timerConfig,
-    });
+    this.fakeTimers = new FakeTimers({config, global: global as any});
   }
 
   setup() {

packages/jest-environment-node/src/index.ts

@@ -12,15 +12,9 @@ import {installCommonGlobals} from 'jest-util';
 import {JestFakeTimers as FakeTimers} from '@jest/fake-timers';
 import {JestEnvironment} from '@jest/environment';
 
-type Timer = {
-  id: number;
-  ref: () => Timer;
-  unref: () => Timer;
-};
-
 class NodeEnvironment implements JestEnvironment {
   context: Context | null;
-  fakeTimers: FakeTimers<Timer> | null;
+  fakeTimers: FakeTimers | null;
   global: Global.Global;
   moduleMocker: ModuleMocker | null;
 
@@ -54,30 +48,7 @@ class NodeEnvironment implements JestEnvironment {
     installCommonGlobals(global, config.globals);
     this.moduleMocker = new ModuleMocker(global);
 
-    const timerIdToRef = (id: number) => ({
-      id,
-      ref() {
-        return this;
-      },
-      unref() {
-        return this;
-      },
-    });
-
-    const timerRefToId = (timer: Timer): number | undefined =>
-      (timer && timer.id) || undefined;
-
-    const timerConfig = {
-      idToRef: timerIdToRef,
-      refToId: timerRefToId,
-    };
-
-    this.fakeTimers = new FakeTimers({
-      config,
-      global,
-      moduleMocker: this.moduleMocker,
-      timerConfig,
-    });
+    this.fakeTimers = new FakeTimers({config, global});
   }
 
   setup() {

packages/jest-environment/src/index.ts

@@ -26,7 +26,7 @@ export declare class JestEnvironment {
   constructor(config: Config.ProjectConfig);
   constructor(config: Config.ProjectConfig, context: EnvironmentContext);
   global: Global.Global;
-  fakeTimers: FakeTimers<unknown> | null;
+  fakeTimers: FakeTimers | null;
   moduleMocker: ModuleMocker | null;
   runScript(
     script: Script,
@@ -162,10 +162,6 @@ export interface Jest {
    * retries is exhausted. This only works with `jest-circus`!
    */
   retryTimes(numRetries: number): Jest;
-  /**
-   * Exhausts tasks queued by setImmediate().
-   */
-  runAllImmediates(): void;
   /**
    * Exhausts the micro-task queue (usually interfaced in node via
    * process.nextTick).
@@ -246,4 +242,7 @@ export interface Jest {
    * every test so that local module state doesn't conflict between tests.
    */
   isolateModules(fn: () => void): Jest;
+
+  getRealSystemTime(): number;
+  setSystemTime(now?: number): void;
 }

packages/jest-fake-timers/package.json

@@ -12,7 +12,11 @@
   "dependencies": {
     "@jest/types": "^24.5.0",
     "jest-message-util": "^24.5.0",
-    "jest-mock": "^24.5.0"
+    "jest-mock": "^24.5.0",
+    "lolex": "^3.1.0"
+  },
+  "devDependencies": {
+    "@types/lolex": "^3.1.1"
   },
   "engines": {
     "node": ">= 6"

packages/jest-fake-timers/src/__tests__/__snapshots__/jestFakeTimers.test.ts.snap

@@ -1,7 +1,3 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`FakeTimers runAllTimers warns when trying to advance timers while real timers are used 1`] = `
-"A function to advance timers was called but the timers API is not mocked with fake timers. Call \`jest.useFakeTimers()\` in this test or enable fake timers globally by setting \`\\"timers\\": \\"fake\\"\` in the configuration file. This warning is likely a result of a default configuration change in Jest 15.
-
-Release Blog Post: https://jestjs.io/blog/2016/09/01/jest-15.html"
-`;
+exports[`FakeTimers runAllTimers warns when trying to advance timers while real timers are used 1`] = `"A function to advance timers was called but the timers API is not mocked with fake timers. Call \`jest.useFakeTimers()\` in this test or enable fake timers globally by setting \`\\"timers\\": \\"fake\\"\` in the configuration file"`;