Since jest 26, you can use the ‘modern’ fakeTimers implementation (see article here) wich supports the method jest.setSystemTime. beforeAll(() => { jest.useFakeTimers(‘modern’); jest.setSystemTime(new Date(2020, 3, 1)); }); afterAll(() => { jest.useRealTimers(); }); Note that ‘modern’ will be the default implementation from jest version 27. See documentation for setSystemTime here.
CLI options are documented and also accessible by running the command jest –help. You’ll see the option you are looking for : –runInBand.
Updated answer: using async / await leads to cleaner code. Old code below. I’ve successfully solved this problem by combining the following elements: Mock out the promise and make it resolve immediately Make the test asynchronous by marking the test function async After simulating the click, wait until the next macrotask to give the promise … Read more
You have to re-import or re-require your module. Check the doc or this issue for more information: https://github.com/facebook/jest/issues/3236 https://facebook.github.io/jest/docs/en/jest-object.html#jestresetmodules describe(‘MyModule’, () => { beforeEach(() => { jest.resetModules() }); describe(‘init’, () => { const myModule = require(‘./MyModule’); it(‘not throws exception when called’, () => { expect(() => myModule.init()).not.toThrow(); }); }) describe(‘do’, () => { const myModule … Read more
You need to store your mocked component in a variable with a name prefixed by “mock”. This solution is based on the Note at the end of the error message I was getting. Note: This is a precaution to guard against uninitialized mock variables. If it is ensured that the mock is required lazily, variable … Read more
#1 Using Jest This is how I use the Jest mock callback function to test the click event: import React from ‘react’; import { shallow } from ‘enzyme’; import Button from ‘./Button’; describe(‘Test Button component’, () => { it(‘Test click event’, () => { const mockCallBack = jest.fn(); const button = shallow((<Button onClick={mockCallBack}>Ok!</Button>)); button.find(‘button’).simulate(‘click’); expect(mockCallBack.mock.calls.length).toEqual(1); … Read more
In Jest you have to pass a function into expect(function).toThrow(<blank or type of error>). Example: test(“Test description”, () => { const t = () => { throw new TypeError(); }; expect(t).toThrow(TypeError); }); Or if you also want to check for error message: test(“Test description”, () => { const t = () => { throw new … Read more
The timeout you specify here needs to be shorter than the default timeout. The default timeout is 5000 and the framework by default is jasmine in case of jest. You can specify the timeout inside the test by adding jest.setTimeout(30000); But this would be specific to the test. Or you can set up the configuration … Read more
Yes, it is possible from jest@25.4.0. From this version, there is a native support of esm, so you will not have to transpile your code with babel anymore. It is not documented yet, but according to this issue you have to do 3 easy steps to achieve that (At the time of writing this answer): … Read more
Similar to what others have said, but instead of trying to mock the DOM yourself, just use JSDOM: // __mocks__/client.js import { JSDOM } from “jsdom” const dom = new JSDOM() global.document = dom.window.document global.window = dom.window Then in your jest config: “setupFiles”: [ “./__mocks__/client.js” ],