What are the best practices for mocking async calls in tests?

What are the best practices for mocking async calls in tests?

When mocking async calls, it's important to ensure that your mocks accurately simulate the behavior of the real async functions. This includes handling promises correctly and ensuring that your tests wait for the async operations to complete.

Can you give me an example of how to mock an async function?

Sure! If you're using Jest, you can use jest.fn() to create a mock function. For example:

const fetchData = jest.fn().mockResolvedValue('data');

This mocks an async function that resolves with 'data'.

What should I avoid when mocking async calls?

Avoid mocking too much of the implementation details. Focus on the behavior instead. Also, ensure that your mocks don't introduce flakiness in your tests.

How do I test error handling in async calls?

You can mock the async function to reject with an error. For example:

const fetchData = jest.fn().mockRejectedValue(new Error('Error fetching data'));

Then, test how your code handles that error.