What are the differences between mocking and spying in testing?

What are the differences between mocking and spying in testing?

Mocking and spying are both techniques used in testing to isolate and verify the behavior of components. Mocking creates a fake version of a component that simulates its behavior, while spying allows you to track calls to a real component without altering its behavior.

Can you give me an example of when to use each?

Sure! Use mocking when you want to simulate a component that is not yet implemented or is difficult to set up. Use spying when you want to observe how a real component is used in a test without changing its behavior.

Are there any libraries that help with mocking and spying?

Yes, popular libraries like Jest and Sinon provide built-in support for both mocking and spying, making it easier to implement these techniques in your tests.

What are the benefits of using these techniques?

The benefits include improved test isolation, easier debugging, and the ability to test components in isolation without relying on their dependencies.