How do I dynamically change Unity Cloud environments for development builds?

Environments in Unity Cloud are very helpful for testing services in a way that doesn't impact the players playing your game.

However, remembering to toggle which environment your application is targeting is a tiresome process, and you might want to have different environments used when building for different circumstances.

Solution: 

You can use a combination of conditional compilation and setting the environment in code as demonstrated here to have your code conditionally switch environments when it is built.

       var options = new InitializationOptions();
       #if UNITY_EDITOR || DEVELOPMENT_BUILD
       options.SetEnvironmentName("dev");
       #endif
       await UnityServices.InitializeAsync(options);       

This means that if you're working from inside the Unity Editor, or have deliberately selected to build your game as a development build, it will now default to using the "dev" environment.