The task of system testing is to check out the errors in the program as thoroughly as possible and improve the reliability of the software system. Its purpose is to check how the system "does". This stage can be divided into three steps: module test, test each module program is correct; Assembly test, test whether the interface between modules is correct; Validation test, test whether the entire software system meets the user's functional and performance requirements. After the test finds the problem, it also needs to find out the cause and location of the error through debugging, and finally correct it