@jest/fake-timers
Advanced tools
@jest/fake-timers is a package that provides fake timer functions for Jest, a popular JavaScript testing framework. It allows you to control the passage of time in your tests, making it easier to test code that relies on timers, such as setTimeout, setInterval, and Date.
Mocking setTimeout and setInterval
This feature allows you to mock setTimeout and setInterval functions, enabling you to control the passage of time in your tests. The code sample demonstrates how to use jest.useFakeTimers() to mock the timers and jest.advanceTimersByTime() to fast-forward time.
const { jest } = require('@jest/globals');
jest.useFakeTimers();
setTimeout(() => {
console.log('This will be logged after 1 second');
}, 1000);
jest.advanceTimersByTime(1000); // Fast-forward time by 1 second
// Output: 'This will be logged after 1 second'Mocking Date
This feature allows you to mock the Date object, enabling you to control the current date and time in your tests. The code sample demonstrates how to use jest.useFakeTimers('modern') to mock the Date object and jest.setSystemTime() to set a specific date and time.
const { jest } = require('@jest/globals');
jest.useFakeTimers('modern');
const now = Date.now();
console.log(now); // Outputs the current timestamp
jest.setSystemTime(new Date('2020-01-01'));
const newNow = Date.now();
console.log(newNow); // Outputs the timestamp for 2020-01-01Clearing timers
This feature allows you to clear mocked timers, ensuring that the associated callbacks are not executed. The code sample demonstrates how to use clearTimeout() to clear a setTimeout timer.
const { jest } = require('@jest/globals');
jest.useFakeTimers();
const timeoutId = setTimeout(() => {
console.log('This will not be logged');
}, 1000);
clearTimeout(timeoutId);
jest.advanceTimersByTime(1000); // Fast-forward time by 1 second
// No outputSinon is a popular standalone test spies, stubs, and mocks library for JavaScript. It provides similar functionalities to @jest/fake-timers, including the ability to mock timers and control the passage of time. However, Sinon is not tied to any specific testing framework and can be used with various testing libraries.
Lolex is a standalone library for creating fake timers and controlling the passage of time. It provides similar functionalities to @jest/fake-timers, such as mocking setTimeout, setInterval, and Date. Lolex can be used independently or integrated with other testing frameworks.
24.9.0
[expect] Highlight substring differences when matcher fails, part 1 (#8448)[expect] Highlight substring differences when matcher fails, part 2 (#8528)[expect] Improve report when mock-spy matcher fails, part 1 (#8640)[expect] Improve report when mock-spy matcher fails, part 2 (#8649)[expect] Improve report when mock-spy matcher fails, part 3 (#8697)[expect] Improve report when mock-spy matcher fails, part 4 (#8710)[expect] Throw matcher error when received cannot be jasmine spy (#8747)[expect] Improve report when negative CalledWith assertion fails (#8755)[expect] Improve report when positive CalledWith assertion fails (#8771)[expect] Display equal values for ReturnedWith similar to CalledWith (#8791)[expect, jest-snapshot] Change color from green for some args in matcher hints (#8812)[jest-snapshot] Highlight substring differences when matcher fails, part 3 (#8569)[jest-core] Improve report when snapshots are obsolete (#8665)[jest-cli] Improve chai support (with detailed output, to match jest exceptions) (#8454)[*] Manage the global timeout with --testTimeout command line argument. (#8456)[pretty-format] Render custom displayName of memoized components (#8546)[jest-validate] Allow maxWorkers as part of the jest.config.js (#8565)[jest-runtime] Allow passing configuration objects to transformers (#7288)[@jest/core, @jest/test-sequencer] Support async sort in custom testSequencer (#8642)[jest-runtime, @jest/fake-timers] Add jest.advanceTimersToNextTimer (#8713)[@jest-transform] Extract transforming require logic within jest-core into @jest-transform (#8756)[jest-matcher-utils] Add color options to matcherHint (#8795)[jest-circus/jest-jasmine2] Give clearer output for Node assert errors (#8792)[jest-runner] Export all types in the type signature of jest-runner (#8825)[jest-cli] Detect side-effect only imports when running --onlyChanged or --changedSince (#8670)[jest-cli] Allow --maxWorkers to work with % input again (#8565)[babel-plugin-jest-hoist] Expand list of whitelisted globals in global mocks (#8429)[jest-core] Make watch plugin initialization errors look nice (#8422)[jest-snapshot] Prevent inline snapshots from drifting when inline snapshots are updated (#8492)[jest-haste-map] Don't throw on missing mapper in Node crawler (#8558)[jest-core] Fix incorrect passWithNoTests warning (#8595)[jest-snapshots] Fix test retries that contain snapshots (#8629)[jest-mock] Fix incorrect assignments when restoring mocks in instances where they originally didn't exist (#8631)[expect] Fix stack overflow when matching objects with circular references (#8687)[jest-haste-map] Workaround a node >=12.5.0 bug that causes the process not to exit after tests have completed and cancerous memory growth (#8787)[docs] Replace FlowType with TypeScript in CONTRIBUTING.MD code conventions[jest-leak-detector] remove code repeat (#8438)[docs] Add example to jest.requireActual (#8482)[docs] Add example to jest.mock for mocking ES6 modules with the factory parameter (#8550)[docs] Add information about using jest.doMock with ES6 imports (#8573)[docs] Fix variable name in custom-matcher-api code example (#8582)[docs] Fix example used in custom environment docs (#8617)[docs] Updated react tutorial to refer to new package of react-testing-library (@testing-library/react) (#8753)[docs] Updated imports of react-testing-library to @testing-library/react in website (#8757)[jest-core] Add getVersion (moved from jest-cli) (#8706)[docs] Fix MockFunctions example that was using toContain instead of toContainEqual (#8765)[*] Make sure copyright header comment includes license (#8783)[*] Check copyright and license as one joined substring (#8815)[docs] Fix WatchPlugins jestHooks.shouldRunTestSuite example that receives an object (#8784)[*] Enforce LF line endings (#8809)[pretty-format] Delete obsolete link and simplify structure in README (#8824)[docs] Fix broken transform link on webpack page (#9155)FAQs
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The npm package @jest/fake-timers receives a total of 21,071,922 weekly downloads. As such, @jest/fake-timers popularity was classified as popular.
We found that @jest/fake-timers demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 3 open source maintainers collaborating on the project.
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