When you're building things for the huge audience the Web allows, a very real fear that you have is a software glitch that prevents data from displaying correctly. When developing projects on a tight timeline, testing is an aspect that often gets neglected as the deadline gets closer and closer, and often things need to be viewed by other people (editors, managers, and the like) even earlier, emphasizing output over process in turn. Let me be clear--if you want to ensure that your visualizations are high-quality, you need to take steps to ensure that they are well-tested and functioning properly. On some level, doing this is an exercise in managing complexity.
The following chart depicts project complexity over time. As you can see, complexity increases somewhat exponentially as time goes on. Adding more team members, more lines of code, and/or more dependencies increases the project's complexity dramatically. Meanwhile, the step-chart depicts...