jest-file-snapshot

jest-file-snapshot

Jest matcher to write snapshots to a separate file instead of the default snapshot file used by Jest. Writing a snapshot to a separate file means you have proper syntax highlighting in the output file, and better readability without those pesky escape characters. It's also useful if you have binary content.

Installation

npm install --save-dev jest-file-snapshot

or

yarn add --dev jest-file-snapshot

Usage

Extend Jest's expect:

import { toMatchFile } from 'jest-file-snapshot';

expect.extend({ toMatchFile });

Then use it in your tests:

it('matches content of file on disk', () => {
  expect(content).toMatchFile();
});

The content passed can be of type string or a Buffer. The comparison be done using Buffer.equals() instead of === if a Buffer is passed.

The matcher takes two optional arguments:

• filepath: path to the file whose content should be matched, e.g. expect(content).toMatchFile(path.join(__dirname, 'output.md'))
• options: additional options object for the matcher, with following properties:
  • diff: options for jest-diff
  • fileExtension: optional file extension to use for the snapshot file.

You should also exclude the output files from Jest's watcher so that updating the snapshot doesn't re-run the tests again.

For example, by default toMatchFile uses a folder named __file_snapshots__ which you can exclude by adding the following under the jest key in package.json:

"watchPathIgnorePatterns": [
  "__file_snapshots__"
]

Credits

• jest-image-snapshot

Contributing

Make sure your code passes the unit tests, ESLint and TypeScript. Run the following to verify:

yarn test
yarn lint
yarn typescript

To fix formatting errors, run the following:

yarn lint -- --fix