jestrestoreAllMocks

jestrestoreAllMocks is a function provided by the Jest testing framework. Its primary purpose is to restore all mocks created by Jest to their original implementations. This is particularly useful in scenarios where you have used Jest's mocking capabilities to replace functions or modules with test doubles, and you need to ensure that these changes are reverted before subsequent tests run.

When tests are executed, Jest's mocking functions, such as jest.fn(), jest.spyOn(), and jest.mock(), alter the behavior of the code under test. If these mocks are not reset, they can persist between tests, leading to unexpected behavior and test failures. jestrestoreAllMocks provides a convenient way to clean up these mocks after each test or a group of tests.

It is often used in conjunction with test setup and teardown hooks. For example, in a typical Jest test file, you might call jestrestoreAllMocks() in an afterEach or afterAll hook. This ensures that any mocks set up for a specific test or test suite are automatically removed, leaving the original code intact for the next test. This practice promotes test isolation, meaning that each test should not depend on the state or side effects of other tests.

Using jestrestoreAllMocks() helps maintain a predictable testing environment by guaranteeing that each test begins with the original state of your modules and functions, unless explicitly mocked for that specific test. This prevents "test pollution" and makes debugging much simpler.