Chapter 6. Developing a Performance Test Plan

Performance tests require a test plan. Before writing the first test script or starting the first test run, you need to develop test goals and a plan for obtaining the desired measurements. Well-designed tests tell you if the site achieves key goals, as well as how the site needs to grow in the future as traffic increases . A poorly designed test usually provides misleading information.

In Chapter 5, we discussed the different performance issues and priorities of various web sites. Keep these differences in mind as you begin your test planning. While understanding throughput and response time is important, some web sites require additional testing to determine the maximum logged-on users they support. Likewise, each site needs realistic test scenarios in order to accurately stress key components such as caches, databases, and application servers. A good test plan manages all of these requirements.

Beyond the measures, we need goals before entering the performance test. Performance tests, as more thoroughly described in Chapter 11, cycle through an iterative process of testing, resolving bottlenecks, and retesting. Without goals, the cycle of testing and resolution often continues indefinitely. You must identify the point of diminishing returns for your testing before you start.

This chapter discusses how to interpret rough performance requirements to develop test goals. Also, we discuss the basics of response time measurements, as well as testing for maximum logged-on users. Beyond setting goals, the chapter covers strategies for test implementation. For very large sites, generating the full, peak user load proves impossible . We cover strategies for validating web site performance by testing small portions of the site. Finally, we discuss how to use the performance test for planning future site growth. Properly designed tests uncover the weakest points in the web site and teach us how to better manage these weaknesses as the site grows.