If we look at the various annotations available in JUnit, @RunWith is one of the most important annotations. This annotation is used to specify which runner class will be used to run the test. In other words, it tells JUnit what to do with the tests. For example, we can use the @RunWith annotation to specify that we want to use a particular junit runner class. The @RunWith annotation can also be used to specify how many times a test should be run. For example, we can use the @RunWith annotation to specify that a test should be run 10 times. We can also use the @RunWith annotation to specify that a test should be run on a particular platform. For example, we can use the @RunWith annotation to specify that a test should be run on Windows.