What is Jest mocking and how do I use it?

What is Jest mocking and how do I use it?

Jest mocking is a technique used in testing to replace real implementations with mock functions. This allows you to isolate the code being tested and control its behavior.

Can you give me an example of how to mock a function in Jest?

Sure! You can use jest.fn() to create a mock function. For example:

const myMock = jest.fn();
myMock();
console.log(myMock.mock.calls.length); // Output: 1

What about mocking modules?

To mock a module, you can use jest.mock(). For instance:

jest.mock('./myModule');
import myModule from './myModule';
myModule.mockImplementation(() => 'mocked value');

Are there any best practices for using mocks?

Yes! Some best practices include keeping mocks simple, avoiding over-mocking, and ensuring your tests remain readable.