Learning from our tests
Our tests are a rich source of feedback on our design. As we make decisions, we write them as test code. Seeing this code – the first usage of our production code – brings into sharp focus how good our proposed design is. When our design isn’t good, the AAA sections of our test will reveal those design issues as code smells in the test. Let’s try to understand in detail how each of these can help identify a faulty design.
A messy Arrange step
If the code in our Arrange step is messy, our object may be difficult to create and configure. It may need too many parameters in a constructor or too many optional parameters left as null in the test. It may be that the object needs too many dependencies injected, indicating that it has too many responsibilities or it might need too many primitive data parameters to pass in a lot of configuration items. These are signals that the way we create our object might benefit from a redesign.
