Boris Beizer, identified five phases of a tester’s mental life:
Phase 0: There’s no difference between testing and debugging. Other than in support of debugging, testing has no purpose.
Phase 1: The purpose of testing is to show that the software works.
Phase 2: The purpose of testing is to show that the software doesn’t work.
Phase 3: The purpose of testing is not to prove anything, but to reduce the perceived risk of the software not working to an acceptable value.
Phase 4: Testing is not an act. It is a mental discipline that results in low-risk software without much testing effort.
