How can I separate testing and production data in my Firebase Database?

Each Firebase project includes only one JSON tree for data. Best practices dictate that tests should be run on a separate database from production data. What is the simplest way to achieve this?

Some things I considered:

• Using multiple sub-trees within the same project for testing and production - This seems messy and the testing and production data are hardly separated.
• Setting up multiple Firebase projects for testing and production - This seems like the best answer from this question related to Android. But I'm not sure how to set up multiple GoogleService-Info.plist files in Xcode and switch between them based on my app's Configuration.