Does Test Driven Development take the focus from Design?
agile, architecture, tdd
Solution
No.
If done right, Test Driven Development IS your design tool.
I hope you forgive me for linking to my own blog entry, wherein I discuss the pitfalls of Test Driven Development that went wrong simply because developers treated their tests as, merely, tests.
In a previous project, devs used a highly damaging singleton pattern that enforced dependencies throughout the project, which just broke the whole thing when requirements were changed:
TDD was treated as a task, when it should have been treated as an an approach. [...]
There was a failure to recognize that TDD is not about tests, it’s about design. The rampant case of singleton abuse in the unit tests made this obvious: instead of the test writers thinking “WTF are these singleton = value; statements doing in my tests?”, the test writers just propagated the singleton into the tests. 330 times.
The unfortunate consequence is that the build server-enforced testing was made to pass, whatever it took.
Test Driven Development, done right, should make developers highly aware of design pitfalls like tight coupling, violations of DRY (don't repeat yourself), violations of SRP (Single Responsibility Principle), etc.
If you write passing code for your tests for the sake of passing your tests, you have already failed: you should treat hard to write tests as signposts that make you ask: why is this done this way? Why can't I test this code without depending on some other code? Why can't I reuse this code? Why is this code breaking when used by itself?
Besides if your design is truly clean, and your code truly maintainable why is it not trivial to write a test for it?
Problem
I have mixed feelings about TDD. While I believe in testing I have a issues with the idea of the test driving my development effort. When you code to satisfy some tests written for an interface for requirements you have right now, you might shift your focus from building maintainable code, from clean design and from sound architecture. I have a problem with driven not with testing. Any thoughts?