Agile Testing: A Practical Guide for Testers and Agile Teams

It is important to think about the whole system and not just the application itself. For example, the network is often the bottleneck, because it can’t handle the increased throughput. What about the database? Will it scale? Will the hardware you are using handle the new loads being considered? Is it simple just to add new hardware, or is it the bottleneck?

Janet’s Story

In one organization I was recently working in, their customer base had grown very quickly, and the solution they had invested in had reached its capacity due to hardware constraints. It was not a simple matter of adding a new server, because the solution was not designed that way. The system needed to be monitored to restart services during peak usage.

To grow, the organization had to actually change solutions to accommodate its future growth, but this was not recognized until problems started to happen.

Ideally, the organization would have replaced the old system before it was an issue. This is an example of why it is important to understand your system and its capability, as well as future growth projections.

—Janet

You will need to go outside the team to get the answers you require to address scalability issues, so plan ahead.

Performance and Load Testing

Performance testing is usually done to help identify bottlenecks in a system or to establish a baseline for future testing. It is also done to ensure compliance with performance goals and requirements, and to help stakeholders make informed decisions related to the overall quality of the application being tested.

Load testing evaluates system behavior as more and more users access the system at the same time. Stress testing evaluates the robustness of the application under higher-than-expected loads. Will the application scale as the business grows? Characteristics such as response time can be more critical than functionality for some applications.

Grig Gheorghiu [2005] emphasizes the need for clearly defined expectations to get value from performance testing. He says, “If you don’t know where you want to go in terms of the system, then it matters little which direction you take (remember Alice and the Cheshire Cat?).” For example, you probably want to know the number of concurrent users and the acceptable response time for a web application.

Performance and Load-Testing Tools

After you’ve defined your performance goals, you can use a variety of tools to put a load on the system and check for bottlenecks. This can be done at the unit level, with tools such as JUnitPerf, httperf, or a home-grown harness. Apache JMeter, The Grinder, Pounder, ftptt, and OpenWebLoad are more examples of the many open source performance and load test tools available at the time of this writing. Some of these, such as JMeter, can be used on a variety of server types, from SOAP to LDAP to POP3 mail. Plenty of commercial tool options are available too, including NeoLoad, WebLoad, eValid LoadTest, LoadRunner, and SOATest.

See the bibliography for links to sites where you can research tools.

Use these tools to look for performance bottlenecks. Lisa’s team uses JProfiler to look for application bottlenecks and memory leaks, and JConsole to analyze database usage. Similar tools exist for .NET and other environments, including .NET Memory Profiler and ANTS Profiler Pro. As Grig points out, there are database-specific profilers to pinpoint performance issues at the database level; ask your database experts to work with you. Your system administrators can help you use shell commands such as top, or tools such as PerfMon to monitor CPU, memory, swap, disk I/O, and other hardware resources. Similar tools are available at the network level, for example, NetScout.

You can also use the tools the team is most familiar with. In one project, Janet worked very closely with one of the programmers to create the tests. She helped him to define the tests needed based on customer’s performance and load expectations, and he automated them using JUnit. Together they analyzed the results to report back to the customer.

Establishing a baseline is a good first step for evaluating performance. The next section explores this aspect of performance testing.

Baseline

Performance tuning can turn into a big project, so it is essential to provide a baseline that you can compare against new versions of the software on performance. Even if performance isn’t your biggest concern at the moment, don’t ignore it. It’s a good idea to get a performance baseline so that you know later which direction your response time is headed. Lisa’s company hosts a website that has had a small load on it. They got a load test baseline on the site so that as it grew, they’d know how performance was being affected.

Performance Baseline Test Results