Testing involves finding errors in a program. The goal is to assume a program contains errors and test to find as many as possible. Different testing techniques include white box testing by developers and black box testing by testers. Testing levels include unit, integration, system, and user acceptance testing. Developers and testers have different goals - developers want code to work while testers try to make code fail. Good development practices from a tester's view include doing own acceptance tests, fixing bugs, writing helpful error messages, and not artificially adding bugs. Good relationships between project managers, developers and testers help ensure quality.