expect.addSnapshotSerializer(serializer)

You can call expect.addSnapshotSerializer to add a module that formats application-specific data structures.

For an individual test file, an added module precedes any modules from snapshotSerializers configuration, which precede the default snapshot serializers for built-in JavaScript types and for React elements. The last module added is the first module tested.

import serializer from 'my-serializer-module';
expect.addSnapshotSerializer(serializer);
// affects expect(value).toMatchSnapshot() assertions in the test file

If you add a snapshot serializer in individual test files instead of to adding it to snapshotSerializers configuration:

• You make the dependency explicit instead of implicit.
• You avoid limits to configuration that might cause you to eject from create-react-app.
  See configuring Jest for more information.