Scheduler-test.js — react Source File

Source Code

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @emails react-core
 * @jest-environment node
 */

'use strict';

let Scheduler;
let runtime;
let performance;
let cancelCallback;
let scheduleCallback;
let requestPaint;
let shouldYield;
let NormalPriority;
let SchedulerFeatureFlags;

// The Scheduler implementation uses browser APIs like `MessageChannel` and
// `setTimeout` to schedule work on the main thread. Most of our tests treat
// these as implementation details; however, the sequence and timing of these
// APIs are not precisely specified, and can vary across browsers.
//
// To prevent regressions, we need the ability to simulate specific edge cases
// that we may encounter in various browsers.
//
// This test suite mocks all browser methods used in our implementation. It
// assumes as little as possible about the order and timing of events.
describe('SchedulerBrowser', () => {
  beforeEach(() => {
    jest.resetModules();
    runtime = installMockBrowserRuntime();
    jest.unmock('scheduler');

    performance = global.performance;
    Scheduler = require('scheduler');
    cancelCallback = Scheduler.unstable_cancelCallback;
    scheduleCallback = Scheduler.unstable_scheduleCallback;
    NormalPriority = Scheduler.unstable_NormalPriority;
    requestPaint = Scheduler.unstable_requestPaint;
    shouldYield = Scheduler.unstable_shouldYield;
    SchedulerFeatureFlags = require('../SchedulerFeatureFlags');
  });

  afterEach(() => {
    delete global.performance;

    if (!runtime.isLogEmpty()) {
      throw Error('Test exited without clearing log.');
    }
  });

  function installMockBrowserRuntime() {
    let hasPendingMessageEvent = false;
    let isFiringMessageEvent = false;
    let hasPendingDiscreteEvent = false;
// ... (292 more lines)