Programming Jakarta Struts, Second Edition

Performance Versus Load Testing

There are many different types of software testing: functional, unit, integration, white box, black box, regression, and so on. Performance and load testing are among the most important types of testing, but they usually get the least amount of attention. There are two general reasons for this neglect. The first reason is that developers typically wait until the very end of the development cycle to start testing the performance of the application, and the end of the cycle is when you have the least amount of time for testing. It is true, however, that it’s not always practical to conduct performance testing during every phase of development. Early phases tend to focus on the architecturally significant pieces, and there may not be enough of the application built to test its performance. You should, however, gather some preliminary performance measurements as early as possible.

Another reason that performance and load testing don’t get much attention is that they’re honestly hard to do. While there are many tools on the market, both free and commercial, it’s not always easy to use these tools to detect problems. The tools must be able to simulate many simultaneous users of a system, but that involves understanding what virtual users are,^[13] what the different threading models are, and how they affect performance and load. Also, you must be able to look at the results and determine whether or not they are acceptable. All of this can be overwhelming ...