15.3 What s Missing?

15.3 What's Missing?

When I started this book project, I had hoped to be able to cover all important unit-testing problems in one book this size. My research work during writing and the large number of comments obtained from the reviewers have shown that I was wrong. Each technical discipline we dealt with in a separate chapter led to a new problem that would have deserved another chapter.

Issues that fell through the selection funnel include unit tests in the context of XML and XSLT, Web services, SOAP, asynchronous messaging, numerous JUnit expansions, object-oriented databases, and many more. The fact that the number of uncovered testing problems increases rather than decreases is mainly due to SUN themselves, as they continually rig out Java with new APIs and components. Therefore, a fat paper file full of ideas has to wait for another book.

However, there are still questions that remain unanswered because I lacked either experience, theoretical material or understanding—and sometimes all three things. I want to address two of these loose ends very briefly:

• Test-first development with simple design and continuous refactoring works best when the complete code is created and changed within one single team. As soon as code gets out, we have to provide for additional documentation, for example, in the form of DBC contracts, and a more stable interface policy. Although extensive test suites are still required, they assume a different (additional) task.

• The question of whether the more important role of unit tests in test-driven development is quality assurance or design control remains unanswered. And using the test-first approach to improve the design is merely based on empirical experience and is not scientifically substantiated. This also holds true for many—if not all—other software development approaches.

The test-first approach is not a fully explored terrain, even at the end of this book. I look forward to intensive and fruitful discussions with you, readers, and to reading many more books about this topic.