Testing

Test-driven development means that you will write tests for virtually every bit of code. It also means that you will write the tests first. The tests are a means of specifying what the code needs to do. After writing the corresponding code, the tests are run to ensure that the code does what the tests specify.

Each class you code will have a corresponding test class. In Figure 1.1, StudentTest is the test class for the production class Student.

Figure 1.1. Test and Production Class

StudentTest will have to create objects of class Student, send messages to these objects, and prove that once all the messages have been sent, things are as expected. StudentTest is thus dependent on Student, as shown by the navigable association in the diagram. Conversely, Student is not dependent on StudentTest: The production classes you build should know nothing about the tests written for them.