Replace Development with Design

by Kofi Sarfo 27. May 2010 17:21

About seven years after everyone else got it I think I may have finally gotten it too. That final letter in TDD may be about Design as anything else!

I've never written anything in Java so the offer to deconstruct/reconstruct and deploy a Java EE website based on Struts sounded a death march. We brought in a dedicated contractor who struggled some with Tomcat instances and lock down. Difficulties correctly called.

We needed to work out which code (including SQL) was being called for each page on a public facing website. I didn't fancy clicking through the website and scribbling down the execution path, which someone suggested and I'd no idea whether there existed anything that allows bytecode instrumentation without modifying the Java source. A quick look at Spring and AspectJ indicated that neither are particularly lightweight. 

This looked promising though: Javassist is a load-time reflective system for Java. IBM developerworks has a handy guide to aspect-oriented changes with Javassist. Still not sure, however, how to tie method calls to database calls.

In the end I wrote some code generation utility to add logging for both method calls and database calls (via OJDBC), using Regex to identify each. The key thing here was that no single method in the C# tool was written without first writing a test. Not only is this the first thing I've ever written with 100% code coverage but I managed also to maintain the discipline needed to avoid squeezing in some code without first having a failing test. Each initial test was followed with a passing test using the very simplest solution, writing a second failing test by varying parameters, before completing the implementation.

Once applied to production code I then realised that I'd made no design decisions. Absolutely none! This is something I'd never previously considered. I expect this very same light bulb went on too for many folks almost a decade ago. If you only ever write the next method required the design just emerges. Also, the simplest possible solution in this case meant there were no redundant lines to delete at the end. Just very satisfying indeed.

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Design

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