Snapshot testing in React Native - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is snapshot testing in React Native?

Snapshot testing captures the rendered output of a component and saves it as a file. Later, it compares the current output to the saved snapshot to detect unexpected changes.

beginner

How do you create a snapshot test for a React Native component?

You render the component using a test renderer, then use expect(tree).toMatchSnapshot() to save or compare the snapshot.

beginner

Why is snapshot testing useful in mobile app development?

It helps catch UI changes early by comparing the current UI output to a saved version, preventing accidental visual bugs.

intermediate

What should you do if a snapshot test fails because of an intentional UI change?

Review the changes and if they are expected, update the snapshot file by running the test command with the update flag (e.g., jest -u).

intermediate

Name one limitation of snapshot testing.

Snapshot tests can pass even if the UI looks wrong, because they only compare output text, not actual rendered visuals or user experience.

What does a snapshot test compare in React Native?

A The rendered component output to a saved snapshot file

B The app's performance metrics

C The network requests made by the app

D The app's database contents

Snapshot tests compare the current rendered output of a component to a previously saved snapshot file to detect changes.

Which command updates snapshot files when UI changes are intentional?

A jest --watch

B jest -u

C npm start

D react-native run-ios

The jest -u command updates snapshot files to reflect intentional UI changes.

Snapshot testing is best described as:

A Validating backend API responses

B Testing app performance under load

C Testing user interactions manually

D Checking if UI output matches a saved version

Snapshot testing checks if the UI output matches a saved snapshot to catch unexpected changes.

What tool is commonly used for snapshot testing in React Native?

A Jest

B Redux

C Expo

D Firebase

Jest is the testing framework commonly used for snapshot testing in React Native.

If a snapshot test fails unexpectedly, what should you do first?

A Ignore the failure

B Delete the snapshot file

C Review the UI changes to confirm if they are intentional

D Restart the device

You should review the UI changes to confirm if they are intentional before updating snapshots.

Explain how snapshot testing helps maintain UI consistency in React Native apps.

Think about how saving and comparing UI output can catch bugs.

Describe the steps to write and update a snapshot test for a React Native component.

Focus on the test code and commands used.