Ruby Refactorings

I think I accidentally discovered two new refactorings today, Extract Mixin and Replace Mixin With Class. (I'll make detailed writeups in a day or two.) This morning I found myself in central Gothenburg with nothing to do for an hour before a meeting, so I ducked into a cafe, had a cup of tea, and began refactoring Test::Unit::XML.

If you have had a look at the code in the assertions mixin, xml_assertions.rb, in version 0.1.4, you'll notice that it is fairly heavyweight, weighing in at more than 220 lines of code. This is a fairly large chunk of code, and all of it is for a single assertion, assert_xml_equal. A big part of that code is for comparing different types of REXML nodes, REXML::Element, REXML::Text, and so on.

The node comparison code was split into fairly small methods, so it wasn't too shabby, it was just that it was located in the wrong place. It made sense to move that code to a class of its own.

I did consider moving it to a mixin module, but in the end I decided against it. The main reason is that the XML assertions in Test::Unit::XML are mixed in with the Test::Unit::TestCase class. I don't want to pollute Test::Unit::TestCase with a lot of methods that don't need to be there.

However, extracting the comparison methods into a mixin of its own was a logical first step. I created a mixin module, moved the XML comparison methods there, added an include statement to the xml_assertions.rb file, and ran my test suite. Everything worked.

The second step was to replace the new comparison mixin with a class. First, I wrote a comparison class, and included the comparison mixin. Second, I changed the XML assertion module in xml_assertions.rb so that it instantiated the comparison class and called its methods instead of using the comparison mixins directly. Third, I ran the tests, and they worked. Fourth, I removed the include statement that included the comparison mixins in the assertions module. Step five was to move the comparison methods into the comparison class and remove the comparison mixin. Finally, I ran the tests again, and everything was OK.

Comments

Post a Comment

Popular posts from this blog

Waterfall vs. Agile: Battle of the Dunces or A Race to the Bottom?

Image
The major software methodology wars since the mid 1950’s. Someone was wrong on the Internet, so here we go… In a recent HBR article, It’s Time to End the Battle Between Waterfall and Agile , the author sets up a false premise: There is a war between Waterfall methodology and Agile. The war must end. And finally, you can combine the approaches to get the best of both worlds. This sounds good, but the article is based on a misunderstanding of both Waterfall and Agile. Also, there is no war between Waterfall methodology and Agile. There can’t be, because Waterfall methodology does not exist! Waterfall is a name for large projects that failed in the 1960’s. Waterfall was never a methodology, but a failure to apply the methodologies that existed back then. As I will show towards the end of this article, at least one of the “successful” Waterfall projects mentioned in the HBR article was neither successful, nor a Waterfall project. I got invaluable help from Alistair Cockburn. He fact che...
Read more

Performance Evaluations, Business Strategy, and Agile Methodologies

Image
It is performance evaluation time in many companies. This can be stressful, both to the people being evaluated, and the people doing the evaluation. In companies adopting agile software development methods, the tension can be extraordinary. Individual performance evaluations run counter to agile philosophy, which emphasizes team performance over individual performance. However, managers and corporate leaders need to take a few steps back, and consider the impact performance evaluations have on the organization as a whole. Especially now, in the midst of a recession, it is important to look at a companies current policies to see if they can be improved, or if they are actually holding the company back. So, how can a manager evaluate policy? Performance evaluation policies can serve as an excellent example. I'll confine myself to discussing the so-called ‘rank and yank’ methods. These are performance reviews were employees are ranked using a forced ranking system. It usually looks so...
Read more

Agile Requirements Structures, Part 1

Image
If you have worked in large Agile projects or programs, you may have noticed that there is often quite a bit of confusion about requirements, what the requirement types are, their purpose, how to write them, how to use them, and above all, what not to do with them. There are many causes for this confusion. Here are some of the more common I have seen: Nobody in the organization has read up on the requirements model it is using, so everyone makes their own interpretation. The organization deviates from a standard requirements model, but nobody knows which standard model the organization is deviating from, and/or there is no agreement about how they deviate from it. The organization has not documented its own requirements model very well. The organization mixes two or more different requirements models, often without realizing it. The organization has documented its requirements model, but finding the documentation is an epic project in itself, on par with when Henry Sta...
Read more