This library includes functions and forms for working with mocks. A mock is a "fake" function used in place of the real thing during testing to simplify the test and ensure only a single unit and not it’s complex dependencies is being tested. Mocks record all arguments they’re called with and results they return for tests to inspect and verify. Mocks are most useful for testing code that calls procedures with side effects like mutation and IO.
source code: https://github.com/jackfirth/racket-mock