Reverse Engineering Tools

There are a couple of tools that analyze existing code base to extract its design or external behavior. For example, Agitar can analyze your Java bytecode and generate JUnit tests ... Altova can analyze your code to generate the UML diagram.

These reverse engineering tools provide value to legacy application where you have a piece of running production code but very little information about its design, and you have very little test where you can understand its expected behavior. These tools can quickly analyze the code and tell you its observed behavior. It "discover" what the code is current doing and give you a better starting point to do further analysis.
Giving you a better starting point is all it provides. They are typically unable to distinguish between the intended behavior (sitting at a higher level of abstraction) from its actual implementation (sitting at a much lower level). In fact, I doubt if automatically extract the intended behavior is at all possible. The end result is that it swarms you with a lot of low-level, implementation-specific details (because the actual implementation is all it knows) and then you need to manually analyze what is important and what is unimportant to you.

In other words, it gives you a different starting point with a different format (e.g. a set of test methods and class invariants it detects instead of implementation Java code). But it doesn't raise your level of abstraction which I argue has to be done manually anyway. So does it give you a better start ? I think it is better but not too much better. By following a set of code surgery, refactoring technique, we can achieve a much better result. I will share such techniques in later blogs.

Now, is these tools useful for new development ? I don't think so. I am a stronger believer of TDD (Test-Driven-Development) where the test itself should be regarded as the "spec" and so by definition has to be written first and has to be written manually by the application designer. In TDD, you write your test first and write it manually (not generated). You put in all the expected behavior in your test methods, and you also put in Mock object to test its interaction. You diagram your UML model to capture your major classes and methods at a higher abstraction level.