Hello

How often QA engineers are responsible for developing Mock Objects for Unit Testing. So dealing with Mock Objects is just developer job ?. The reason i ask is i'm interested in QA as my career and am learning tools like JUnit , TestNG and couple of frameworks. I just want to know until what level of unit testing is done by developer and from what point QA engineer takes over testing for better test coverage ?

Thanks

Edit : Based on the answers below am providing more details about what QA i was referring to . I'm interested in more of Test Automation rather than simple QA involved in record and play of script. So Test Automation engineers are responsible for developing frameworks ? or do they have a team of developers dedicated in Framework development ? Yes i was asking about usage of Mock Objects for testing from Test Automation engineer perspective.