- Believe that the application will work with the way it supposed to be
This is why QA are paid, to ensure that the application will work with the way it supposed to be, according to every words in the software requirement documents.
- Trust a programmer
Programmers are all big liars. Maybe not all, but most of them are. Never trust these liars.
- Make assumptions
You think out a problem where the application might have a leak. You told the programmer and what they DON'T WANT TO FIX IT because they assume that it would never happened in the real world. According to the Murphy's law, bad things has a big chance to happen.
- Don't know how to make a set of tight test cases
Go grap some testing book and learn from it how to make good test cases.
- Intended to run the tests one time
Software aren't gonna developed once even for a project-based software. A bug might happen in the future and QA has to retest the entire application or at least a module where the changes might take effect.
Mi Mee SDLC