What is a requirement for the classes included in a GUnit test suite?

In a GUnit test suite, classes included must be of the same class type to ensure uniformity in how the tests are executed and managed. This requirement allows the test runner to effectively handle the lifecycle of the tests, as it needs to know the specific behavior expected from the classes under test. When all test classes are of the same type, it simplifies the process of instantiating the tests, running them, and collecting results – all essential for maintaining consistency across test execution.

The other options provided do not align as well with the fundamental principles of a GUnit test suite. While ensuring comprehensive coverage of different application modules is beneficial for testing, it does not necessitate that all included tests be of different types. Compliance with the same test interfaces is relevant for certain testing frameworks, but in this context of a GUnit test suite, the focus is primarily on the class type. Lastly, representing only integration tests would limit the suite to a specific scope of testing, which is not a requirement for creating a diverse and effective test suite.