What are Jest mocks and how do I use them?

What are Jest mocks and how do I use them?

Jest mocks are functions that simulate the behavior of real functions in your tests. They help isolate the code being tested.

Can you show me an example of how to create a mock function?

Sure! You can create a mock function using jest.fn(). For example: const myMock = jest.fn();.

How do I use mocks to test a function that calls another function?

You can use mocks to track calls to the function. For instance, if you have a function fetchData, you can mock it and assert it was called.

What about mocking modules?

You can mock entire modules using jest.mock('moduleName'). This allows you to replace the module's implementation in your tests.