Hello GMC, I am struggling with the whole testing topic in GMS. The way I see it any setup for this would need to take into consideration: Separation of resources just for testing and production resources Testing code should not be included in the final game Developer experience should be pleasant Setup should not be overcomplicated / should be stable across GMS updates I have managed to create a setup that allows me to perform Unit Tests in GMS but it is not perfect as it violates point 4 and point 3 is not the best either (especially in a computer with a low amount of resources). In a nutshell the process I have consists of: A "base" project with all of the production resources except rooms A "main" project that inherits from the "base" project and adds the rooms for the final game A "test" project that inherits from the "base" project and adds the room(s) and other resources for running the tests This solution: Provides complete separation of production resources and test resources as they live in different projects All of the testing code is contained in the "test" project Involves having between two to three IDE instances open if you want to regularly switch between developing production resources and running tests, which is a pain in computers with low resources Consists of a lot of manual hackery with the project files just to allow this setup to be runnable at all, plus I only tested it on non-YYC Windows targets without even performing the export of the game, so it isn't even guaranteed to work across the board Therefore I would like to know what alternatives are there / what other developers are doing in this regard. Thanks in advance! P.S.: I can explain / share an example of my setup if anyone is interested on the internals of it.