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
Create multiple Firebase projects. Each project has its own plist file.
FIRApp
has a custom configuration option. Download the plist for your testing/debug project, rename it and load like below.
#if DEBUG
NSString *filePath = [[NSBundle mainBundle] pathForResource:@"GoogleService-Info-dev" ofType:@"plist"];
FIROptions *options = [[FIROptions alloc] initWithContentsOfFile:filePath];
[FIRApp configureWithOptions:options];
#else
[FIRApp configure];
#endif
A more detailed explanation can be found here