A Comprehensive Guide to Performance Testing


June 22, 2020



Performance testing is a critical priority and an essential part of testing software. It helps companies avoid long load times or even crashes that lead to the unfortunate loss of users. With the increasing interactivity of applications and requests to them from users, the load on the server is growing and requires a high level of service. Performance testing has become one of the most important testing stages, allowing the emulation of user queries for comparison with performance indicators that affect the application’s stability and tolerance.

Various types of performance testing help to evaluate the behavior of the application for a given expected load and assess the behavior of the system when the standard load is exceeded. In order to understand the nature of performance testing, it’s important to understand the concept of three W’s: what, why, and when.

What is Performance Testing?

Performance testing is a process of evaluating how a system performs under a specific workload. Performance testing examines the speed, reliability, and size of the application—it is not about finding software bugs or defects. Performance tests serve a diagnostic purpose to view network response times, server request processing times, and user volumes. Non-functional testing is what determines the readiness of a system and ensures that it meets the service levels expected in production.

Why is Performance Testing Important?

Performance testing highlights improvements for the application relative to speed, stability, and scalability before it goes live into production. Any product or an application released to the public without adequate performance testing could suffer from issues that lead to a damaged brand reputation. Success and productivity of an application depend directly on properly conducted performance tests.

When is the Right Time for Performance Testing?

The earlier, the better. During both development and deployment, the application needs to be exposed to end-users of the product architecture. Performance tests focus on components of the application such as web services, microservices, and APIs. The earlier these components are tested, the sooner any anomaly can be detected, lowering the cost of rectification.

Types of Performance testing

To understand how the software will perform on user systems, different types of performance tests need to be conducted.

Load testing

Load testing measures system performance under different workloads as they increase. It simulates either the number of virtual users that might use the application or the number of transactions. The system is monitored to measure response time as the workload increases. Based on response times, this test can help identify potential bottlenecks. This test falls within the parameters of normal working conditions. Load testing also helps to understand whether it is necessary to adjust the size of an application’s architecture.

Stress testing

This type of testing is used to measure system performance outside of the parameters of normal working conditions. It evaluates the behavior of the system at its peak of activity. The goal is to measure software stability when the system is given more users or transactions that it can handle. Stress testing helps to identify the point of failure and how software recovers from it.

Spike testing

Spike testing evaluates software performance under quickly and repeatedly increased workloads. This testing measures system activity levels when they are above average. It is testing a number of users and the complexity of actions performed.

Scalability testing

Scalability testing determines the software’s effectiveness under a gradual workload increase. The system’s behavior is monitored as user, load, or data volume is gradually added.

Endurance/Soak testing

This type of testing measures how the software performs with a normal workload over an extended period of time. The goal is to test potential memory leaks and to observe if intense and sustained activity over time shows a potential drop in performance levels.

Volume testing

This type of testing determines the efficiency of software when performance is measured with a large, projected amount of data.

Advantages of Performance Testing

It is critical that performance testing be conducted early and often. A single test will not tell developers all they need to know. It is a collection of repeated and frequent tests that makes performance testing successful. A few important facts to consider:

  • Test as early as possible. Don’t wait until the end of the project.
  • Consider performance testing not only for completed projects but also for individual modules.
  • Test the individual units of database and servers separately as well as together.

Following the guidelines above will reveal important information about the application. This information can help make the application faster, more stable, and help validate the quality of code and functionality. Conducting performance testing provides the following advantages:

  • Validates the fundamental features of the software.
  • Provides a measurement of the speed, accuracy, and stability of the software under stress.
  • Helps to identify discrepancies and improve optimization.

Effective Performance Testing and Success Metrics

An important point to keep in mind is that performance testing is not only about simulating a large number of transactions, it is also to provide insight into how the product will perform once it has gone live. The best performance tests are those that allow for quick and accurate analysis to identify all performance problems as well as their causes. Before starting the tests, success metrics should be clearly defined. In general, these parameters are:

  • Amount of time the processor spends running non-idle threads
  • Use of a computer’s physical memory for the processing
  • Number of bits per second used by the network interface
  • The time the disk is busy with read/write requests
  • Number of bytes used by a process that cannot be shared with others (used to measure memory leaks)
  • Amount of virtual memory used
  • Number of pages written or read to disk to resolve hardware page defects
  • The overall processing rate of faulty pages by the processor
  • The average number of hardware interruptions the processor receives/processes each second
  • Response times
  • The rate at which a computer/network receives requests per second
  • Number of user requests satisfied by pooled connections
  • Maximum number of sessions that can be simultaneously active
  • Number of SQL statements handled by cached data instead of expensive I/O operations
  • Maximum wait times
  • Number of threads currently running/active
  • The return rate of unused memory in the system (garbage collector)


Digital transformation is driving businesses to accelerate the pace of designing new services, applications, and features, raising the bar on application performance. Users no longer tolerate having to stare at loading animations or splash screens for too long. They will simply abandon a service provider if the app is not responsive enough. Performance testing helps prevent bottlenecks from forming and enables teams to develop more efficient code that ultimately makes an application run flawlessly.

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Authored By

Ramin Mammadov, QA Manager

Ramin Mammadov

QA Manager

Meet our Experts

Ramin Mammadov, QA Manager

Ramin Mammadov

QA Manager

Ramin Mammadov is a Quality Assurance Manager at Levvel. He is responsible for building and leading QA organization, providing insight and expertise on the best QA practices and approach for digital transformation, and supporting defect-free application software. Ramin comes to Levvel with 15+ years of experience in financial industry where he implemented and maintained the Quality Control Process by providing knowledge and expertise in quality assurance methods, tools, and technology. Ramin holds and M.A from Michigan State University and B.A. from Baku State University.

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