Updated for Jest 27+ For jest 27+, you can also use process.nextTick: await new Promise(process.nextTick); (Thanks to Adrian Godong in the comments) Original Answer Here’s a snippet that waits until pending Promises are resolved: const flushPromises = () => new Promise(setImmediate); Note that setImmediate is a non-standard feature (and is not expected to become standard). … Read more
The following method worked for me. This approach allowed me to test some code that should work both in the browser and in Node.js, as it allowed me to set window to undefined. This was with Jest 24.8 (I believe): let windowSpy; beforeEach(() => { windowSpy = jest.spyOn(window, “window”, “get”); }); afterEach(() => { windowSpy.mockRestore(); … Read more
If an ES6 module directly exports two functions (not within a class, object, etc., just directly exports the functions like in the question) and one directly calls the other, then that call cannot be mocked. In this case, funcB cannot be mocked within funcA the way the code is currently written. A mock replaces the … Read more
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
Without using any other libraries: import * as axios from “axios”; // Mock out all top level functions, such as get, put, delete and post: jest.mock(“axios”); // … test(“good response”, () => { axios.get.mockImplementation(() => Promise.resolve({ data: {…} })); // … }); test(“bad response”, () => { axios.get.mockImplementation(() => Promise.reject({ … })); // … }); … Read more
Edit: Several years have passed and this isn’t really the right way to do this any more (and probably never was, my bad). Mutating an imported module is nasty and can lead to side effects like tests that pass or fail depending on execution order. I’m leaving this answer in its original form for historical … Read more
An alternative solution can be importing the module into its own code file and using the imported instance of all of the exported entities. Like this: import * as thisModule from ‘./module’; export function bar () { return ‘bar’; } export function foo () { return `I am foo. bar is ${thisModule.bar()}`; } Now mocking … Read more