If you have Babel in your stack, you can fix this in the right way using babel-jest Just do npm i –save-dev babel-jest and in your jest settings file add: “moduleNameMapper”: { “^.+\\.(css|less|scss)$”: “babel-jest” }
Jest runs test suites in parallel by default. However, the machine that the tests are running on only has a single port 3000 (or port 4000, etc.) This means that if you tell your app to listen on a port, and then start multiple concurrent processes, there will be a port collision and Jest will … Read more
That issue is caused by many updates inside Component. I got the same issue, this would solve the issue. await act( async () => mount(<App />));
You need to find the StyledButton in the Button component before asserting the props // Button.test.js import React from ‘react’; import { shallow } from ‘enzyme’; import Button from ‘../../components/Button/Button’; import { StyledButton } from ‘./styled’ describe(‘Component: Button’, () => { const minProps = { text: ”, size: ”, }; it(‘renders a button in size … Read more
It looks like you’re on the right track. Just to make sure everyone’s on the same page for this answer, let’s get some terminology out of the way. Mock: A function with behavior controlled by the unit test. You usually swap out real functions on some object with a mock function to ensure that the … Read more
You can use jest.resetModules() in beforeEach method to reset the already required modules beforeEach(() => { jest.resetModules() process.env = { …OLD_ENV }; delete process.env.NODE_ENV; });
I had the same issue when updating my react app to jest 28. The issue was the missing jest-environment-jsdom package which was not yet necessary in jest 27. See https://jestjs.io/docs/28.x/upgrading-to-jest28
I solved this issue using: npm uninstall -g jest npm install -g jest npm cache clean npm install
Ok so I found the solution here. Basically, had to add 2 things to the webpack config under module.rules: { test: /\.m?js/, type: “javascript/auto”, }, { test: /\.m?js/, resolve: { fullySpecified: false, }, },
Maybe the type of expectation variable and the answer on the right side are different in your case. In my case, the error occurred because I tried to use toBe assertion in an array, and not in the array.length Wrong example: expect(array).toBe(3) Correct example: expect(array.length).toBe(3)