/mock-issue

Primary LanguageHTML

Purpose

To demonstrate the issue with jest.mock()

My Question

After calling jest.mock() to mock a module, how can we restore that module?

I have 2 different tests in App.test.js file. I want to use the mocked module in one test and use the original module in the other test. How to achieve this scenario? Already tried jest.resetAllMocks() and mockClear() without success.

Steps to Reproduce

  1. Clone this repo.
  2. Run yarn to install dependencies.
  3. Run yarn test to run test.
  4. In App.test.js, if there is jest.mock(), the test "1 - with mocked module" will pass but the test "2 - with original module" will fail.
  5. On the other hand, if there is not jest.mock(), the test "1 - with mocked module" will fail but the test "2 - with original module" will pass.

Solutions

1st Option (Implemented in this repo)

From this issue

  1. Add this code into the beginning of the test that we want to restore mockMyModule to the original form

    mockMyModule.mockImplementationOnce(require.requireActual('./myModule').myModule)

    Or using mockImplementation() instead

    mockMyModule.mockImplementationOnce(require.requireActual('./myModule').myModule)

  2. Don't forget to mockReset() if we want other test cases to use the initial jest.mock() version

    mockMyModule.mockReset()

2nd Option

https://stackoverflow.com/a/53166827/6568503

3rd Option

Just make a separate test file. One that uses the mock and the other that doesn't.

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