Question Errors appear after adding assembly reference

I am currently following a tutorial to write unit tests in Play Mode for my game, where the tutorial mentioned that I need to add an assembly reference in my scripts folder. However, the moment I add the assembly reference, there are a few errors "TMPro not found" that would occur. May i know why does this happen?


Without Assembly Definition


With Assembly Definition

 

You need to reference the other assemblies: https://docs.unity3d.com/Manual/Scr...finitionFiles.html#reference-another-assembly