Day 39

Today I enhanced my sorting algorithm which lines up all the tables. First I made the function that compares two tables a little more forgiving. Ultimately I will need to make this comparison a percentage fitting algorithm, so that it will still match tables that are just a tiny bit different. Since FitNesse tests often have collapsible sections, that reveal some test specifics, I also had to make the comparison ignore those collapsed sections.

The biggest task today was to refactor the whole HistoryComparitor class. Most of this I just did myself, extracting method after method, giving names that described to true intent of the code, and abstracting certain repeditive concepts and variables. There was one method I needed help refactoring because it was a bit tricky. This was the same method that had a three level loop, that I described breifly yesterday. The method was actually one algorithm repeated twice for its compliment. Once for the firstTableList and again for the secondTableList. Once we noticed this, we began to implement the Strategy Pattern.
First we created an interface which described what methods we were going to need. Then we implemented that interface in two derivative classes, one for the firstTableList and another for the second.
By extracting the details of the algorithm into two subclasses, we had the power to remove all the duplication and generalize the algorithm such that it worked for both lists. This process made the code much easier to understand and follow, removed duplication and regidity, as well as freed the algorithm to be used elsewhere if needed.

The really cool part was that we kept the tests passing the entire time. At anypoint during our refactoring process we could have released the code and it would have worked. This is an essential skill that I must master. The refactoring was slow and careful, but vastly increased my understanding of both my own code and the power of the tests I wrote. The Strategy Pattern was pretty cool to.