Stories about Software


TDD Chess Game Part 9: God Save the Queen

As always, it seems that I’ve let too much time elapse between iterations of this series. This time my excuse was worse than ever. I actually had this video ready to go last Friday or something and then the post was was queued up on Sunday, but I was too tired when I got home on Sunday night to remember to go publish it. Anyway, it’s live now.

Here’s what I accomplish in this clip:

  • Implement Queen with GetMovesFrom()
  • Add more common functionality to Piece base class.

Here are some lessons to take away:

  • For the most part, in the last number of clips things had gone more or less as I expected.  Here you got to see the value of the test suite indicating to me that I was reasoning about the code incorrectly.  I didn’t realize that the GetRadial methods were returning only moves N spaces away rather than up to and including N spaces.  It took some floundering to figure this out and, without red tests telling me things were going haywire, I probably would have plowed ahead for minutes or hours before I realized things weren’t working.
  • Pulling up functionality into a common base class is a way to avoid duplication and make tests go green rapidly, but beware of creating a base class abstraction that’s awkward just to reuse code.  If it seems awkward, it might be worth creating a class that your ancestors use.  So far, the functionality in Piece seems to make sense, but I’ll keep an eye on this.
  • Use Intellisense in a savvy way.  When you notice a few times that what you’re expecting to happen isn’t happening, that’s a yellow (if not red) flag.  Late in the video, this kept happening to me, and it turned out to be because I had spelled “radial” as “raidal” when defining a method.  Typos, incorrect assumptions, etc — often these things can be revealed by the IDE not behaving as expected.
  • Definitely keep track of refactorings you’d like to do in you list.  Treat these as if they were no different than features you want implemented.

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