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Test classpath

During the testing, multiple classpaths are loaded in order to properly set up the testing environment. The task needs to load the test runner, the classes that are being tested, and the test cases. All of them are part of different ClassLoaders, and they have different visibilities in order to properly ensure runtime class loading.

We define the following class loaders:

  • ClassPath (also known as user classpath).
    • Contains the classes that are the subject of the testing.
  • TestRunnerClassPath.
    • Contains the classes for the test runner. The test runner is used to invoke the test cases. (E.g. jUnit, or other testing frameworks)
  • TestClassPath.
    • Contains the classes of the test cases that are being executed.

The above class loaders are in a relation as the following diagram illustrates:

Based on the above, we can see the setup of the class loaders during testing. The ClassPath classloader have access only to the standard JVM classes. It cannot access classes defined in the Test(Runner)ClassPath class loaders.

The TestRunnerClassPath is the one that contains the testing framework. It is responsible for invoking the tests defined in TestClassPath. It can access the classes defined in the package (the saker.nest package), and only the classes with the package prefix of This is order for the test runner to be able to integrate with the API.

The test runner classpath won't be able to access other classes from the saker.nest or runtime.

The TestClassPath can access the classes from ClassPath in order to test them. It can also access the TestRunnerClassPath in order to integrate with the test runner framework. However, it cannot access the classes from the package, or any other transitive parent class loaders.

But how does the TestRunnerClassPath know about the test cases defined in TestClassPath?

The test runner is initialized with the reference to the TestClassPath (this is not displayed in the above diagram). For each test case that is being invoked, the test runner will be passed the name of the test case class. It will then use the ClassLoader for the test class path, and load the test case class for the given name.