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Craftsman Swap Day 4

by: jim | April 17th, 2009 |

Dave Hoover and I got back to the Mad Mimi feature implementation first thing in the morning. Dave had left a failing test the previous afternoon, which was meant to serve as a reminder for where we left off. This technique is great when you need to stop in the middle of what you’re doing, and it works well as long as you know what the next step needs to be. This should help you reestablish the context you were holding when you stopped. Of course, if you’re at a natural break point and the next step isn’t clearly defined, I tend to avoid writing a failing test. Often when I come back to code after a break, I will find a simpler way to approach the problem at hand. I don’t like short-circuiting that process by leading myself towards a solution I saw when I was leaving the code. Anyway, in this case, it was clear where we needed to go, and the failing test got us right back to it.

Mad Mimi has grown organically without any traditional marketing or advertising efforts. That is not to say that there aren’t a lot of users and a lot of data. There are a few database tables that are quite large, and optimizations have been put into place in order for the system to remain responsive. Optimizations are usually going to make a system more complex from a code standpoint. The common advice to avoid premature optimizations is valid exactly because of this. In addition, you’re almost always going to be wrong about where the bottlenecks will occur in your application. If you were to do some premature optimization, you’ll likely find yourself with overly complex code that is still slow. Mimi has been optimized only as needed, and the code base is better for it. One of the optimizations that has been made is limited use of stored procedures.

Stored procedures are not easy to test. The feature we were working on required us to pass an additional parameter into the existing stored procedure. Once we dropped into stored procedure land, we lost the safety net of our tests. So we approached the problem stepwise, in a way “test driving” the stored procedure from the user interface. Fortunately, the stored procedure isn’t overly complex, and executing a couple manual test cases made us confident that the change was correct.

After we finished the feature, it was time to deploy so the customer could test and provide feedback. The deployment process for this project is different than just about every other project I’ve ever been on. Dave has taught the customer, who is not a programmer, how to update from Subversion, run data migrations, start/restart his local web server and BackgroudRB services, etc.. With just a little help, the customer has the system running in development mode on his Mac! Not only that, the customer does the design work for the site. We just added the appropriate view files while implementing the feature with a note for the customer to come through and style the HTML and provide the correct content. The customer is heavily involved in the process, and clearly cares very much about the product. Dave is extremely lucky to have this kind of customer for this project.

1 Response to “Craftsman Swap Day 4”

1. Jake Benilov Says:
   April 19th, 2009 at 04:58 AM

   A great tool for TDDing stored procedures is http://fitnesse.info/dbfit (although whether you want to involve fitnesse as a separate framework is another matter).

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