What are Jest mocking functions and how do I use them?

What are Jest mocking functions and how do I use them?

Jest mocking functions are tools that allow you to replace real functions with mock implementations in your tests. This helps isolate the code being tested.

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

Sure! You can create a mock function using jest.fn(). For example: const myMock = jest.fn(); This creates a mock function that you can use in your tests.

How do I assert that a mock function was called?

You can use expect(myMock).toHaveBeenCalled(); to assert that the mock function was called at least once during the test.

What if I want to mock a specific return value?

You can use myMock.mockReturnValue(value); to specify a return value for your mock function. For example: myMock.mockReturnValue(42);.