Pragmatic Unit Testing in Java with JUnit, 3rd Edition

Writing a First Real Test

An empty test isn’t of much use. Let’s devise a good first test.

You could start with a meaty test that adds a few credit scores, asks for the average, and then ascertains whether or not you got the right answer. This happy path test case—in contrast with negative or error-based tests—is not the only test you’d want to write, though. You have some other cases to consider for verifying arithmeticMean:

• What happens if you add only one credit rating?
• What happens if you don’t add any credit ratings?
• Are there any exceptional cases—conditions under which a problem could occur? How does the code behave under these conditions?

Starting with a happy path test is one choice; you have other options. One is to start with the simplest ...