Automated Web Test

By Floyd Marinescu, Senior Architect,
source: TheServerSide.com

This document explains how to go about performing scalability testing, performance testing, and optimization, in a typical Java 2 Enterprise Edition (J2EE) environment. It describes how TheServerSide.com was able to fix their scalability problems and become one of the fastest java-based portals out there. Read More…

Performance testing and optimizing your application can be pretty challenging. Luckily, there are tools on the market that can make the process easier. By using these tools and following the simple steps in this paper, you should be able to effectively track down the bottlenecks in your system.

TestLoad definition is one of the steps for a performance test plan specification. It is a view account status of the most frequent useresource action against a computing system.

Test Load is generated bycreating virtual users, in a simulation case where the goal is to reflect how users utilize a system. When developers or testers are loadtesting a system, they usually have no numbers that allow creating aload profile. Let us consider a box that contains a processing unit, it can be as specific as a disk subsystem or complex as an entire intranet. If we consider customers C arriving at a rate R to the boxand spending T time utilizing the box, we can say that C=R*T. This is known as Little’s Law. The proof of this simple but important performance law can be found if you searchthe Internet.

For a given system the throughput of a system can bemeasured by dividing the number of users with the time spent in the box(R=C/T). Now let’s assume that users will wait a To time in between requests, which we know as a think time. This is an interval typical for users to interact with the system. So from the C=R*T we can expand and infer that the number of users in think time will be Co=R*To. But the number total of users in such a case will be CTotal = C+Co = R*T + R*To = R(T+To). So CTotal = R(T+To). R=C/(T+To)where T is time spent in the box(response time), To is the average think time,C number of users and R the throughput.

If we had a system with 200 users requesting services with 1600 requestfor 15 minutes and response time average of 2 seconds we can characterize that think times would be C/R-T = 200/1.77 – 2=110.2 seconds average. Now if we wanted to reproduce the same workload characterization without think times in the test environment we could use safely the equivalence of two cases R=C/T or R=CTotal/(T+To). SoC/T=CTotal/T+To. In our hypothetical case above C/2=200/(2+110).2C+110C=400. C=4 users. One could easily extrapolate any workload, provided there was a well known production profile or a performance test goal in mind, and apply the law correctly.
Carlos

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Source: http://blogs.msdn.com/pagtest/