This is very good question for any QA executive and testing guys that when we can stop the testing?
In software world we can not say that particular software is bug free and there is no bug that is why testing process is going continuous. But we always try to give perfect and reliable system but here is the question that how? So there is no predefined explanation for stop the testing process, just like you can not say that when we want to develop the system. Its totally depend upon our needs and requirements. If we need something specific to complete our requirements then we start thinking about new system or application. Same as going with testing process also but with the help of some factors like Time, Budget, Risks, Bugs and etc, we can decide the exit point. May be all these are not applicable in one time always but one of them is playing important role to stop the testing process.
Budget of the any object is playing very important role to define the existence of it. In software development planning we break the budget in different sections that how much we can spend in particular section? So if we have specified budget for testing then we complete the testing in given time. Time and Budget are also important factors to decide the exit point of testing. If we have reviewed and tested all risk area of the system in a given time then we can stop the testing. To decide the exit point of testing phase we check the bug rate also, if bug rate is too low then and if we don’t have enough time and budget then also we can stop the testing.
According to my thinking these are some basic factors to stop the testing. If I am going in wrong way then come and share your thoughts also.