Caching the Firebase Emulator on GitHub Actions

When testing your Firebase application, you need to download the Firebase Emulator. Fortunately, firebase-tools does that automatically for you.

However, when running your tests on a continuous integration environment such as GitHub Actions, you'll see the following warning:

It appears you are running in a CI environment. You can avoid downloading the Pub/Sub Emulator repeatedly by caching the /home/runner/.cache/firebase/emulators directory.

This means, firebase-tools is downloading the Emulator binary every time you run your CI pipeline. You can avoid this by caching the emulator instead:

jobs:
  test:
    runs-on: ubuntu-latest
    env: FIREBASE_EMULATORS_PATH: ${{ github.workspace }}/emulator-cache

    steps:
      - name: Cache firebase emulators
        uses: actions/cache@v2
        with:
          path: ${{ env.FIREBASE_EMULATORS_PATH }}
          key:
            ${{ runner.os }}-firebase-emulators-${{
            hashFiles('emulator-cache/**') }}
        continue-on-error: true

The step above will cache the emulator on GitHub Actions. The next time you run your tests, Firebase won't download the emulator again (unless the binary changed).