Regression testing is used to re-validate modified program and provide confidence that changes does not harm the behavior of the existing code. Test suites grows in size as software evolve, a simple approach of regression testing is re-test all approach in which all the pre-existing test suites are executed on the code but it is too expensive and increase the cost of testing activity. Different problems have been involved with regression testing, e.g. test suites minimization problem, test selection problem, coverage identification problem, test case execution problem, test case maintenance...