Usually, there are many classes to be tested in a Java application. For each Java class in the application you need to write a JUnit test case class comtaining multiple test methods.
You could call a JUnit runner to run each JUnit test case class manually. But you should group all JUnit test case clases into a test suite with JUnit TestSuite. The following code and notes are provided by Varun Chopra and valid for JUnit 3.8 with some corrections.
To group all test case classes together and run them a single unit, you should create a new class named like AllTests.java. In this class you must create a "public static Test suite()" method, which returns a TestSuite object as a container of test case classes.