What is the difference between setupFilesAfterEnv and setupFiles in Jest?

What is the difference between setupFilesAfterEnv and setupFiles in Jest?

In Jest, setupFiles is used to specify files that run before the test framework is installed, while setupFilesAfterEnv runs after the test framework is set up but before the tests are executed.

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

Sure! Use setupFiles for polyfills or global variables needed before Jest starts, and setupFilesAfterEnv for configuring testing libraries like Enzyme or setting up global mocks.

Are there any performance implications of using one over the other?

Generally, there shouldn't be significant performance differences, but using them appropriately can help keep your tests organized and efficient.

What happens if I use both in my Jest configuration?

If you use both, Jest will execute the files in setupFiles first, followed by those in setupFilesAfterEnv. Just ensure that the order makes sense for your setup.