JEST MOCKS INSTALL

It's a good practice to mock API calls in tests, not only because we don't want to call the real API, but also to be able to easily test special cases, such as what happens if the request returns 200 or 404 or fails with the 'Network Error' message. If any difficulties are encountered, only then see if libraries can help solve them. I suggest starting without any library and see if that works well. Jest can swap out timers with functions that allow you to control the passage of time.

JEST MOCKS INSTALL

If you need to test a simple function that makes a request to an API and returns a response - you probably don't need to install and configure additional libraries, just go with the Way #1 and jest.mock() function.Įxternal libraries provide a lot of useful functionality that makes testing harder cases much easier. Jest Guides Timer Mocks Version: 28.1 Timer Mocks The native timer functions (i.e., setTimeout (), setInterval (), clearTimeout (), clearInterval ()) are less than ideal for a testing environment since they depend on real time to elapse. The answer is - it depends on the requirements. In this article we learned two ways to mock Axios using external libraries, so it would be good to know which library is more popular and safer to use.Īccording to the NPM Trends, axios-mock-adapter is much more popular with about 570,000 weekly downloads compared to almost 90,000 for jest-mock-axios:

Confirm that the request was sent to the correct endpoint and that the correct result is returned.

Call the function you are testing ( fetchUsers() in our example).

Create a sample response and mock the call to the specific endpoint by using mock.onGet() function.

Reset the mocked Axios object by calling: mock.reset() after each test in the afterEach hook, so that the state in the mock is cleared and each test starts fresh.Set the Mock Adapter on the default Axios instance: new MockAdapter(axios).

Jest mocks