We perform load testing once we are completed with interface (GUI) testing. Modern system architectures are large and difficult. Whereas one user testing primarily on functionality and user interface of a system component, application testing focuses on performance and reliability of an whole system. For example, a typical application-testing scenario may depict 1000 users logging in at the same time to a system. This gives rise to issues such as what is the response time of the system, does it crash, will it go with different software applications and platforms, can it hold so a lot of hundreds and thousands of users, etc. This is when we set do load and performance testing.