I would whole-heartedly recommend Robert Martin’s clean coding lecture series. It may be many hours of your life, but it is free on youtube and well worth the time. I don’t exactly recall what he says about testing in his lectures, but it’s probably pretty close. If nothing else, it will teach you to critically consider programming structure in the abstract (instead of following formulae), and to write code with the intent for it to be read and maintained by humans.

I think he also has a series that includes “structured programming” (like early return vs deep nesting), but was unable to find it last time I looked for it. I recall having a shocked epiphany when he (i THINK it was Martin) demonstrated the exact way to clean up a function, that started out ugly, and ended up being reduced to literally nothing (the function was removed).