I am still confused why people treat testing as secondary position? Tester are paid less and they hire lower quality engineers. I think testing is as important as any other phase of development, like design or implementation. . . and yeah we do testing of our own code. The only thing I can do in my case is to see that people who change my code may not break basic functionalities. And again about edge cases, try to handle some other left to be seen in production( those which I could not think of due to lack of time) I take care not to leave edge case but sometime cannot do it. I just hope people realise the worth of testing.