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<p>Aslak and I were brought on to a project with the task of refactoring a legacy codebase. A complex application with approximately 30 thousands lines of code, written over a 2 year timeframe by many programmers. The code worked as intended and was actually a success compared to all previous efforts to accomplish the same sort of functionality. The team is <em>somewhat</em> agile and uses CruiseControl for automated builds.</p>

<h3>The Goals</h3>
<p>We had some clear directives from the client:</p>
<ol>
	<li>Disentangle the GUI portion of this codebase (AWT stuff) from the domain layer</li>
	<li>Rewrite the GUI as a remote client</li>
	<li>Expose the domain layer as a clean and reusable public API</li>
</ol>

<p>At first glance, the code didn't look too badly written and Clover was reporting over 60% coverage from approximately 1100 Junit tests. Hmm... Diving into the test suite usually seems like a good starting point to figure out where to start.</p>

<h3>Problematic Unit Tests</h3>
<p>To my dismay, there were some serious issues with the way that the unit tests were written. I should say <em>so-called</em> unit tests, cause there were some major problems to address:</p>

<ul>
	<li>First of all, the test suite was taking about 10-15 minutes to execute.</li>
	<li>As a result, nobody in the team was running the suite on a regular basis except cruise control.</li>
	<li>Suite only passing in forked JVM mode, because of excessive use of statics requiring a pristine runtime. Executing the suit in-process reveals almost all clobber each other in non-deterministic ways.</li>
	<li>Unable to run suite in IntelliJ, because of the aformentioned issue with in-process execution, and because of hundreds of dependencies on test files (xml, db, properties, etc.) to be in the right place on the filesystem.</li>
	<li>About 20 singletons (oh cursed pattern!) and a lot of static utility classes</li>
	<li>Hundreds of mock, dummy, and faux subclasses. Tons of duplication and very confusing.</li>
</ul>

<p>The majority of those tests weren't actually unit tests at all. Sure, they all extended JUnit TestCase, but most of them did some sort of file I/O, many included calls to Thread.sleep(), and during their execution there would be about 20-30 AWT windows popping up and flashing stuff in my face. As a matter of fact, they were <em>system tests</em> masquerading as unit test.</p>