Create a Firebase project and add an Android or IOS app to it. You'll be given the option to download a google-services.json(Android) or GoogleService-Info.plist(IOS) file which should be placed in android/app/google-services.json or ios/Runner/GoogleService-Info.plist respectively.
If you're on Android you'll also need to create a keystore and reference the keystore via the file android/key.properties
flutter run --release --flavor prod -t lib/main_prod.dart
flutter run --release --flavor dev
flutter run --release -t lib/main_prod.dart
flutter run --release
flutter analyze
flutter test