unity-testability

To isolate game logic from Unity APIs for unit testing, you should move pure C# logic out of MonoBehaviour classes into separate assemblies. This separation allows you to test core mechanics independently of the Unity engine lifecycle.

EditMode tests run outside the Unity runtime and are used for testing pure C# logic, while PlayMode tests run inside the Unity engine and are used for testing MonoBehaviour behavior and Unity API integrations.

You should move logic that does not directly require Unity API calls out of MonoBehaviour classes. Isolating state calculations and data processing into pure C# scripts allows them to be tested in EditMode without engine dependencies.

You can test hard-to-test MonoBehaviour logic by extracting the internal algorithms into pure C# classes. This allows you to verify the behavior in EditMode tests without the overhead of running the full Unity game runtime.

A limitation of isolating Unity logic is that code heavily reliant on the Unity API lifecycle, such as physics or coroutines, cannot be fully isolated. You must determine which parts require PlayMode tests and which can move to pure C#.