What are Jest snapshots and how do they compare?

What are Jest snapshots and how do they work?

Jest snapshots are a feature in the Jest testing framework that allows you to capture the rendered output of a component and save it as a reference. When you run your tests, Jest compares the current output to the saved snapshot to check for changes.

How do I create a snapshot in Jest?

To create a snapshot in Jest, you can use the toMatchSnapshot() method in your test. For example, if you're testing a React component, you would render the component and then call expect(component).toMatchSnapshot();.

What happens if the snapshot changes?

If the snapshot changes, Jest will fail the test and indicate that the output has changed. You can then review the changes and decide whether to update the snapshot by running jest --updateSnapshot.

Are there any best practices for using Jest snapshots?

Yes, some best practices include keeping snapshots small and focused, updating them only when necessary, and using them for components with stable output to avoid frequent changes.