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Beware Of Micro-Fragmentation

While watching Neal Ford’s terrific “Agile Engineering Practices” video series, I paid close attention to the segment in which he interactively demonstrated the technique of Test Driven Development (TDD). At the end of his well-orchestrated example, which was to design/write/test code that determines whether an integer is a perfect number, Mr. Ford presented the following side-by-side summary comparison of the resulting “traditional” Code Before Test (CBT) and “agile” TDD designs.

Ford TDD Example

As expected from any good agilista soldier, Mr. Ford extolled the virtues of the TDD derived design on the right without mentioning any downside whatsoever. However, right off the bat, I judged (and still do) that the compact, cohesive, code-all-in-close-proximity CBT design on the left is more readable, understandable, and maintainable than the micro-fragmented TDD design on the right. If the atomic code in the CBT isPerfect() method on the left ended up spanning much more space than shown, I may have ended up agreeing with Neal’s final assessment that the TDD result is better – in this specific case. But I (and hopefully you) don’t subscribe to this, typical-of-agile-zealots, 100% true, assertion:

TDD Improves

The downside of TDD (to which there are, amazingly, none according to those who dwell in the TDD cathedral), is eloquently put by Jim Coplien in his classic “Why Most Unit Testing Is Waste” paper:

If you find your testers (or yourself) splitting up functions to support the testing process, you’re destroying your system architecture and code comprehension along with it. Test at a coarser level of granularity. – Jim Coplien

As best I can, I try to avoid being an absolutist. Thus, if you think the TDD generated code structure on the right is “better” than the integrated code on the left, then kudos to you, my friend. The only point I’m trying to make, especially to younger and less experienced software engineers, is this: every decision is a tradeoff. When it comes to your intimate, personal, work habits, don’t blindly accept what any expert says at face value – especially “agile” experts.

TDD DDT

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  1. January 19, 2015 at 9:01 am

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