Why do you test? Is is because you want to prevent errors on a deployment affecting the visitor? Is it because you simply want to know that the software does what it needs to do? Or maybe you want to get to know the software a bit better?
Hopefully, in this day and age, your main software tests are automated. Running before a commit, running in the deployment pipeline and running on a testing environment. Repetitive jobs need automation and testing fits that mantra very well. This article is relevant for automated testing, although for certain topics you could use a manual testing perspective as well. If you like.