What is the Difference Between Similar But Different Things, Terms, and Objects

What is the Difference between Winrunner, Silkperformer, Loadrunner and Qtp

There are two ways to test different applications, manual and automated. In case of manual testing we see the application from a user’s point of view. On the other hand for automated testing, we use different tools like winrunner, silkperformer, loadrunner and Qtp.