Contents  Introduction  The Basic Tenet  Ten Rules  Ten Rules (cont.)  Printable version

6. Rewrite all prototyping code from scratch. Sometimes you may quickly prototype a new feature to see if it will be viable. Often this is done by sacrificing code quality in the name of rapid development. If you eventually decide to keep the feature, it is very tempting to simply tack on some basic error checking to the prototyping code. Don't fall into this trap. If you weren't writing the code originally with quality as a priority, scrap the prototyping code, and re-implement the feature from scratch. Rapidly prototyped features that slip into the final product are a major source of bugs because they are not subject to the same quality standards as the rest of the code.
   
   
7. Set QA objectives at the beginning of every project. Studies have shown that developers who set reasonable QA goals will usually achieve them. Decide in advance if your product must be fast, small, feature-rich, intuitive, scalable, etc. Then prioritize those objectives. When designing the interface code for an upcoming game, I decided that my top three priorities were to make it beginner-intuitive, fast, and fun, in that order. Consequently, my game's interface isn't as graphically rich as other games, but it is easier to use and faster than any other game of its type. Whenever you have to make a design decision, keep your objectives in mind. If you do not set clear QA goals, then you are doomed to accept the results of random chance.
   
   
8. Don't rush debugging work. Fully 50% of all bug fixes are done incorrectly the first time, often introducing new bugs in the process. Never experiment by simply changing "x-1" to "x+1" to see if that will do the trick. Take the time to understand the source of the bug. Long ago when I was a boy scout and had to put out a campfire, the Scoutmaster would sometimes test my thoroughness by asking me to put my hand in the ashes. I learned very quickly how to put out a fire so well that I had complete confidence it was 100% extinguished. When you find a defect, it means your code is on fire. As long as the defect remains, any new code you write will add fuel to that fire. Whenever you find a defect, drop everything to fix it, and don't move on until you are 100% confident that your fix is correct. If you don't take the time to do it right the first time, when will you find the time to do it over?
   
   
9. Treat the quality of your code at the same level of importance as the quality of your product. Rate your code on a scale of one to ten for overall quality. The first time I did this, I rated my 30,000-line project as a four. I rewrote the worst of the code until I reached an eight overall. It was one of the best investments of time I ever made because I was then able to add new features at double my previous rate. The quality of your code is highly indicative of the quality of your product. You may find as I have that your best selling products also receive your highest ratings for code quality.
   
   
10. Learn from every bug; each one represents a mistake that you made. Learn why you made each mistake, and see if you can change something about your development practices to eliminate it. Over the years I have adopted many simple coding practices that allow me to avoid common bugs that used to plague me. There are many types of bugs that I now never encounter because my coding style makes it physically impossible for me to introduce them.
    
    

Each of these rules represents a simple concept, but their combined benefits are significant. You will achieve higher progress visibility, avoiding the situation of being "99% done" for the last 80% of your development time. Higher quality will make your products easier to maintain and less expensive to support. You will spend less time debugging old code and more time writing new code. And most importantly, it actually takes less time to write high-quality code than it does to write low-quality code, so you will save a great deal of time on overall development. If you have never developed products with a zero-defect philosophy from day one, its adoption can reduce your development time for new products by 30% or more while simultaneously improving product quality.