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Snapshot Testing

What is Snapshot Testing?

Snapshot testing is a type of testing that takes a snapshot of the output of a function or component and compares it to a previously saved snapshot.

Benefits of Snapshot Testing

Benefits of Snapshot Testing

  • Ensures that UI components and APIs behave as expected
  • Detects visual regressions
  • Reduces the need for manual testing
  • Improves collaboration between developers and testers

How Snapshot Testing Works

How Snapshot Testing Works

  1. A snapshot is taken of the output of a function or component.
  2. The snapshot is saved to a file.
  3. When the test is run again, the output is compared to the saved snapshot.
  4. If the output has changed, the test fails.

Snapshot Testing in Different Frameworks

Snapshot Testing in Different Frameworks

  • Jest
  • Cypress
  • Puppeteer
  • Playwright

Jest Snapshot Testing

Jest Snapshot Testing

import {toMatchSnapshot} from 'jest-snapshot';
test('Button renders correctly', () => {
  const button = renderer.create(<Button />);
  toMatchSnapshot(button.toJSON());
});

Writing Snapshot Tests

Writing Snapshot Tests

  • Use descriptive snapshot names.
  • Test different scenarios and edge cases.
  • Keep snapshots up to date with changes to the code.

Updating Snapshots

Updating Snapshots

  • When the output of a function or component changes, the snapshot should be updated.
  • To update a snapshot, run the test with the --updateSnapshots flag.

Best Practices for Snapshot Testing

Best Practices for Snapshot Testing

  • Use snapshots wisely.
  • Keep snapshots organized.
  • Review snapshots regularly.

Limitations of Snapshot Testing

Limitations of Snapshot Testing

  • Snapshots can be brittle.
  • Snapshots can be time-consuming to maintain.
  • Snapshots are not always reliable.

Next Up: Mutation Testing

Next Up: Mutation Testing

Mutation testing is a type of testing that helps to identify parts of code that are not properly tested.

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