Assessing interface changes with snapshot testing

In the .projenrc.ts file, update the input object to ProjenBlueprint with the files you want to snapshot. For example:

{
  ....
  blueprintSnapshotConfiguration: {
    snapshotGlobs: ['**', '!environments/**', '!aws-account-to-environment/**'],
  },
}

Resynthesize the blueprint to create TypeScript files in your blueprint project. Don’t edit the source files since they’re maintained and regenerated by Projen. Use the following command:

yarn projen

Navigate to the src/snapshot-configurations directory to view the default-config.json file with an empty object. Update or replace the file with one or more of your own test configurations. Each test configuration is then merged with the project’s defaults.json file, synthesized, and compared to snapshots when testing. Use the following command to test:

yarn test

The first time you use a test command, the following message is displayed: Snapshot Summary › NN snapshots written from 1 test suite. Subsequent test runs verify that the synthesized output hasn’t changed from the snapshots and display the following message: Snapshots: NN passed, NN total.

If you intentionally change your blueprint to produce a different output, then run the following command to update the reference snapshots:

yarn test:update