jest hangs indefinitely, runs no tests
This happens to me too but it’s intermittent, very frustrating though. I have discovered a workaround which is to run using the –runInBand flag, which just runs tests in the same thread: jest –runInBand
babel-jest
Mocking `document` in jest
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” ],
What is the difference between babel-core and @babel/core?
Since Babel 7 the Babel team switched to scoped packages, so you now have to use @babel/core instead of babel-core. But in essence, @babel/core is just a newer version of babel-core. This is done to make a better distinction which packages are official and which are third-party.
`regeneratorRuntime` is not defined when running Jest test
In case you are using a setupTests.js file you can import regenerator-runtime from there: // setupTests.js import ‘regenerator-runtime/runtime’ import Enzyme from ‘enzyme’ import EnzymeAdapter from ‘enzyme-adapter-react-16’ Enzyme.configure({ adapter: new EnzymeAdapter() }) Then you can import setupTests.js to every test file or better yet, in your package.json just add setupFilesAfterEnv to the jest config: // … Read more
Mocking globals in Jest
As every test suite run its own environment, you can mock globals by just overwriting them. All global variables can be accessed by the global namespace: global.navigator = { onLine: true } The overwrite has only effects in your current test and will not effect others. This also a good way to handle Math.random or … Read more
Jest won’t transform the module – SyntaxError: Cannot use import statement outside a module
Even though I have tried them separately, I haven’t tried them together (transform and transformIgnorePatterns). So this jest configuration solved my issue: “jest”: { “preset”: “ts-jest”, “testEnvironment”: “node”, “transform”: { “node_modules/variables/.+\\.(j|t)sx?$”: “ts-jest” }, “transformIgnorePatterns”: [ “node_modules/(?!variables/.*)” ] }, My mistakes were: Not using transform and transformIgnorePatterns together. And defining babel-jest as the transformer instead of … Read more
Does Jest support ES6 import/export?
From my answer to another question, this can be simpler: The only requirement is to configure your test environment to Babel, and add the ECMAScript 6 transform plugin: Step 1: Add your test environment to .babelrc in the root of your project: { “env”: { “test”: { “plugins”: [“@babel/plugin-transform-modules-commonjs”] } } } Step 2: Install the … Read more
How to resolve “Cannot use import statement outside a module” in jest
Also using Babel, Typescript and Jest. Had the same failure, driving me crazy for hours. Ended up creating a new babel.config.js file specifically for the tests. Had a large .babelrc that wasn’t getting picked up by jest no matter what i did to it. Main app still uses the .babelrc as this overrides babel.config.js files. … Read more