The Firebase emulator has made writing firebase functions, and firebase in general, fun again. It’s a lot more productive and the edit/build/test cycle in seconds.
Previously it was hard, although not impossible, to have production, development, and test databases in Firebase. Configuring them to work with an Android app is very time-consuming and something that doesn’t need to be done anymore as the emulator as it just slots in and the data can be setup for any type of test.