Whatever this file exports if what will be imported when calling jest.mock('src/my-module') without a factory provided.Īs much as possible, try to go with the spyOn version. For instance if you were to import the file src/my-module.js, and wanted a specific factory for it in every test, you can create a file named src/_mocks_/my-module.js.

It is also possible to write this factory in a specific file. If you don't importing the module will just return an empty object.

For instance:Īs you can see, you can use the second parameter to provide a factory so that the import return something. clearAllMocks()Īnother approach to mocking with Jest is to use jest.mock. Globally to affect all existing mocks you've created: jest.

Directly on a mocked function: myMockedFunction.mockClear.mockRestore - Restoring the function actually removes the mock, and restore the original implementation.Īll these functions can be used in two different ways:.Of course it also implies everything mockClear implies. All mocked implementation or return value will be forgotten. mockReset - reseting a mock returns the mock to a fresh state, just like if you just called spyOn on the function.It can be useful if you want to start counting calls after some point in your test. mockClear - clearing a mock means clearing the history of calls that already have been stored in the mock.When clearing mocks, you have 3 possible functions you can call: Here we prevented the actual call to fetch using mockReturnValue ( mockImplementation can be used too), and we restore all existing mocks to their initial state before every test run. The mock itself will still record all calls that go into and instances that come from itself – the only difference is that the implementation will also be executed when the mock is called.Enter fullscreen mode Exit fullscreen mode mockFn.mockImplementation(fn) Īccepts a function that should be used as the implementation of the mock. The restoreMocks configuration option is available to restore mocks automatically before each test. Thus you have to take care of restoration yourself when manually assigning jest.fn(). This is useful when you want to mock functions in certain test cases and restore the original implementation in others.īeware that mockFn.mockRestore() only works when the mock was created with jest.spyOn(). mockFn.mockRestore() ĭoes everything that mockFn.mockReset() does, and also restores the original (non-mocked) implementation. The mockReset configuration option is available to reset mocks automatically before each test. (Note that resetting a spy will result in a function with no return value). This is useful when you want to completely reset a mock back to its initial state. mockFn.mockReset() ĭoes everything that mockFn.mockClear() does, and also removes any mocked return values or implementations. The clearMocks configuration option is available to clear mocks automatically before each tests. Often this is useful when you want to clean up a mocks usage data between two assertions.īeware that mockFn.mockClear() will replace mockFn.mock, not just reset the values of its properties! You should, therefore, avoid assigning mockFn.mock to other variables, temporary or not, to make sure you don't access stale data. Each item in the array is an array of arguments that were passed during the call.įor example: A mock function f that has been called twice, with the arguments f('arg1', 'arg2'), and then with the arguments f('arg3', 'arg4'), would have a mock.calls array that looks like this:Ĭlears all information stored in the, , and arrays. Īn array containing the call arguments of all calls that have been made to this mock function. Returns the mock name string set by calling mockFn.mockName(value).

Jest clear mocks