So far, I really appreciate and enjoy practicing the prime factors kata and the idea of practicing katas in general. I mentioned in my post yesterday that the opportunity to focus wholeheartedly on the fundamentals was beneficial me to in a myriad of ways. That feeling persisted today as I experimented with different ways to complete the kata in order to decrease the time it takes me to complete it.

Apart from gaining proficiency with the VirtualStudio keyboard shortcuts and my own touch typing, through discussion with another apprentice I decided to try and use a C# dictionary in an attempt to reduce duplication and improve speed. However, despite the novelty of this tiny innovation, I wasn’t able to gain much of an advantage. It still required too much set-up and it decreased the readability of the code.

Given that I couldn’t come up with much else in terms of optimization, I became quite fixated on the idea of having one test that iterated through a variable amount of test cases. The dictionary wasn’t doing so I consulted Myles to see if there was another way. As is often the case in programming, there was.

Myles introduced me to some of the benefits of xUnit a testing tool for the .NET framework, as well as some very helpful syntactic sugar in C and a glimpse of LINQ (I’m sure this is an impending post). Anyway, in xUnit uses two types of attributes when creating unit tests [Fact] and [Theory], I really love their reasoning:

Facts are tests which are always true. They test invariant conditions.*

Theories are tests which are only true for a particular set of data.*

So as you might suspect, a theory implies variable data. xUnit has a pretty cool way to handle this with the use of of the [InlineData] attribute. Here’s an example: the finished product of my tests after completing the prime factors kata.

[InlineData (new [] {}, 1)]
[InlineData (new [] {2}, 2)]
[InlineData (new [] {3}, 3)]
[InlineData (new [] {2,2}, 4)]
[InlineData (new [] {2,3}, 6)]
[InlineData (new [ {2,2,2}, 8)]
[InlineData (new [] {3,3}, 9)]
public void TestPrimeFactorsGenerator(List<int> expectedPrimes, int num) {
  Assert.Equal(expectedPrimes, PrimeFactors.Generate(num));

One caveat regarding the use of the [InlineData] attribute: it only works with system defined types. With this new implementation I’m hovering around a 10 minute performance with several more rehearsals I hope to get the entire performance somewhere between 5 and 10.