Best Practices for Application Performance Testing

When done properly, software application performance testing determines if a system meets certain acceptable criteria for both responsiveness and robustness. Before you jump in to testing, though, there are some best practices to remember.

Start by defining test plans that include load testing, stress testing, endurance testing, availability testing, configuration testing and isolation testing. Align these plans with precise metrics in terms of goals, acceptable measurements, thresholds and a plan to overcome performance issues for the best results. Make sure you can triage performance issues in your testing environment; you should analyze issues impacting application performance by examining system functionality under load, not just the indicators of poor performance on the load testing tool side. Leveraging application performance management (APM) tools, which simulate production environments, provide much deeper insights into application functionality, as well as into overall performance under stress or load.

10 Performance Testing Best Practices

1. Test Early and Often

Performance testing is often an afterthought, performed in haste late in the development cycle, or only in response to user complaints. Instead, you should be proactive. Take an agile approach that uses iterative testing throughout the entire development life cycle. Specifically, provide the ability to run performance “unit” testing as part of the development process – and then repeat the same tests on a larger scale in later stages of application readiness. Use performance testing tools as part of an automated pass/fail pipeline, where code that passes moves through the pipeline and code that fails is returned to a developer.

2. Consider Users, Not Just Servers

Performance tests often focus solely on the performance of servers and clusters running software. Don’t forget that people use software, and performance tests also should measure the human element. For instance, measuring the performance of clustered servers may return satisfactory results, but users on a single, troubled server may experience an unsatisfactory result. Tests should take user experience into account, and user interface timing should also be captured along with server metrics.

3. Understand Performance Test Definitions

It’s crucial to have a common definition for the types of performance tests that should be executed against your applications, such as:

• Single User Tests. Testing with one active user yields the best possible performance, and response times can be used for baseline measurements.
• Load Tests. Understand the behavior of the system under average load, including the expected number of concurrent users performing a specific number of transactions within an average hour.
• Peak Load Tests. Understand system behavior under the heaviest anticipated usage for concurrent number of users and transaction rates.
• Endurance (Soak) Tests. Determine the longevity of components, and whether the system can sustain average to peak load over a predefined duration. Monitor memory utilization to detect potential leaks.
• Stress Tests. Understand the upper limits of capacity within the system by purposely pushing it to its breaking point.
• High Availability Tests. Validate how the system behaves during a failure condition while under load. There are many operational use cases that should be included, such as seamless failover of network equipment or rolling server restarts.

5. Build a Complete Performance Model

Measuring your application’s performance includes understanding your system’s capacity. This includes planning what the steady state will be in terms of concurrent users, simultaneous requests, average user sessions and server utilization during peak periods of the day. Additionally, you should define performance goals, such as maximum response times, system scalability, user satisfaction scores, acceptable performance metrics and maximum capacity for all of these metrics.

6. Define Baselines for Important System Functions

In most cases, QA systems performance don’t match production systems performance. Having baseline performance measurements for each system can give you reasonable goals for each testing environment. These baselines provide an important starting point for response time goals, especially if there are no previous metrics, without having to guess or base them on the performance of other applications.

7. Perform Modular and System Performance Tests

Modern applications are incorporate many individual, complex systems, including databases, application servers, web services, legacy systems and so on. All of these systems need to be performance tested individually and together. This helps expose weaknesses, highlight interdependencies and understand which systems you should isolate for further performance tuning.

8. Measure Averages, but Include Outliers

When testing performance, you need to know average response time, but this measurement can be misleading by itself. Be sure to include other metrics, such as 90th percentile or standard deviation, to get a better view of system performance.

KPIs can be measured by looking at average and standard deviations. For example, set a performance goal for the average response time plus one standard deviation beyond it (see Figure 1). In many systems, this improved measurement affects the pass/fail criteria of the test, matching the actual user experience more accurately. Transactions with a high standard deviation can be tuned to reduce system response time variability and improve overall user experience.

9. Consistently Report and Analyze the Results

Performance test design and execution are important, but test reports are, too. Reports communicate the results of your application’s behavior to everyone in your organization, especially project owners and developers. Analyzing and reporting results consistently also helps to determine future updates and fixes. Remember to consider your audience and tailor reports to each audience. Reports for developers should differ from reports sent to project owners, managers, corporate executives and even customers, if applicable.

10. Triage Performance Issues

Providing the results of performance tests is fine, but those results, especially when they demonstrate failure, are not enough. The next step should be to triage the code/application and system performance, and involve all parties: developers, testers and operations personnel involved. Application Monitoring Tools can provide clarity regarding the effectiveness of triage.

Additionally, remember to avoid throwing your software “over the wall” to a separate testing organization, and ensure your QA platforms match production as closely as possible. As with any profession, your efforts are only as good as the tools you use. Be sure to include a mix of manual and automated testing across all systems.