jest mock functions

mockFn.mockClear()

Clears all information stored in the mockFn.mock.calls, mockFn.mock.instances, mockFn.mock.contexts and mockFn.mock.results arrays. Often this is useful when you want to clean up a mocks usage data between two assertions.

mockFn.mockReset()

Does everything that mockFn.mockClear() does, and also replaces the mock implementation with an empty function, returning undefined.

mockFn.mockImplementation(fn)

Accepts a function that should be used as the implementation of the mock.

mockFn.mockReturnValue(value)

Accepts a value that will be returned whenever the mock function is called. Shorthand for: jest.fn().mockImplementation(() => value);

mockFn.mockResolvedValue(value)

Useful to mock async functions in async tests Shorthand for: jest.fn().mockImplementation(() => Promise.resolve(value));

mockFn.mockRejectedValue(value)

Useful to create async mock functions that will always reject Shorthand for: jest.fn().mockImplementation(() => Promise.reject(value));