What are the differences between mocks and stubs in testing?

What are the differences between mocks and stubs in testing?

Mocks and stubs are both used in testing to isolate components, but they serve different purposes. Stubs provide predefined responses to calls made during the test, while mocks are used to verify that certain interactions occurred.

Can you give me an example of a mock and a stub?

Sure! A stub might return a fixed value when a method is called, like returning '5' when a function asks for a user's age. A mock, on the other hand, would check if that method was called with the expected parameters, like ensuring the age method was called with the argument 'John'.

When should I use mocks instead of stubs?

Use mocks when you need to verify interactions and behavior, such as ensuring a method was called. Use stubs when you only need to provide controlled responses without caring about how they were used.

Are there any libraries you recommend for using mocks and stubs?

Yes! For JavaScript, you can use libraries like Jest for mocks and Sinon for stubs. In Python, you might use unittest.mock for both.