We were never taught Test Driven Development at school - no surprise, since I have never even met a single Unity developer that writes tests.

But there's actually a lot of great resources out there! A few of my recommendations:
How to profile and optimize: https://www.youtube.com/watch?v=epTPFamqkZo&list=PLhjeIHf6kJlXbKg2NrCsVHqfWxZ9-ep71&index=8
Performance benchmarking in Unity: https://blog.unity.com/engine-platform/performance-benchmarking-in-unity-how-to-get-started
Learn Unity Test Framework: https://docs.unity3d.com/Packages/com.[email protected]/manual/course/welcome.html

All of them come with sample projects / assets to learn from. Wish me luck on my journey!