The purposes have an overlap in that both serve the purpose of checking correctness.
I don’t get this. Automated tests are full of assertions. If you mean the safetynet that you construct:
you do inspections after changes also. Unit tests have a cost when changing code. You have to maintain them. Functionality changes, functions are removed and created, names of functions change, their signature changes.
I like to work fact-based, empirical research like
shows reviews to be more effective than testing. See 3.5 Review versus testing and 4.1 Cost and benefits
Claims by Uncle Bob and other agilistas about unit testing are not scientifically proved, for me they belong to the realm of pseudoscience. Moral imperatives (f.e. from Uncle Bob “if you don’t do TDD, you are unprofessional”) are unnecessary, and harmfull. I cannot take them serious.
An example of a highly ranked scientist and programmer that is not enthousiast about safetynets:
For more see the interview https://www.informit.com/articles/article.aspx?p=1193856
Read this thread BDD / TDD criticized by the way?
