Scalability Testing is a type of load testing which is also non-functional software testing. This testing methodology involves various applications and infrastructures that are studied for performance under increased or decreased workload. This testing measures the applicant’s ability or performance and deploys its resources to ensure a great user experience.
This test demonstrates the system’s ability to adapt to changes. It ensures that the system adapts to the requirements and offers smooth performance for users while optimizing development and various operational costs.

Scalability testing is performed on a system that can expand until it fails. The use of this testing helps in presuming a system’s weaknesses and vulnerabilities. Furthermore, It pinpoints the exact reasons for a system’s failure during scaling up or down.

How scalability testing is performed

When a developer develops an application, he is only aware of how an application would work in the ideal scenario compared to the real world. With Scalability testing, testers make it easier to handle any defects and help in keeping apps running smoothly. It determines the scale of the real-time potential & full potential of a system. The testers usually draft test scenarios to force the system to meet new requirements. Moreover, they execute the test at regular intervals, document & record the results to detect errors. The obtained data & actionable insights are communicated effectively with the relevant stakeholders.

Design a comprehensive test script that accurately depicts the users’ actions and behavior. Define the variable data that is implemented in the testing process because scalability testing involves data-driven tests. All the data should be accurate for best results; therefore, the run-time data used to interact with the applications during the testing should also be as precise as possible.

Step By Step process

  1. Define a process that can be iterated for executing scalability tests throughout the application tenure.

  2. Determine the domain for Scalability.

  3. Shortlist the software tools needed to run the load test.

  4. Set the testing environment & configure the hardware to execute scalability tests.

  5. Plan the test scenarios (demo) as well as Scalability Tests.

  6. Create and verify the visual script.

  7. Create and verify the load test scenarios.

  8. Execute the tests.

  9. Evaluate the results.

  10. Generate required reports.

What constraints/issues of mobile application are tested in scalability testing

Smartphones coupled with mobile apps usage has increased rapidly and has inevitably caused considerable problems for developers. Every mobile app’s capability, design, and reliability has raised the bar for every user. The users no longer accept simple or substandard mobile apps; therefore, Organisations are putting a robust automation framework to face impossible challenges.

Fragmentation, Usability, and Connectivity are measured in developing a system or an app for mobile. App performance varies significantly between various networks so that users can enjoy flawless performance. Scalability Testing strategy balances the defects during the development of the mobile apps treating usability as a critical priority without neglecting functionality.

What to test in Scalability Testing?

The prominent Scalability Testing Attributes are as follows:

  • Response Time

  • Screen transition

  • Throughput

  • Time Analysis 

  • Performance measurement with several users

  • Network Usage

  • CPU / Memory Usage

  • Web Server Response

  • Performance measurement under load.

Benefits of scalability testing

Many benefits are observed when Scalability Tests are implemented into the development and software testing process.  

1. Improves User experience

Advanced technology has changed users’ expectations and dynamics forever. Therefore, testing scalability helps determine user experience under heavy load when the system is subjected to the stress of upscaling. Scalability Tests help check responsiveness, overall performance, improve application performance metrics, and boost customer experience.

2. Lower Infrastructure Cost

During testing an application or a system, it is essential to observe the expenses involved with upgrading or downgrading. Scaling up apps increases the cost. Even with cloud computing, containers, and serverless computing, one must consider the expenses as they scale up. 

Testing frees the resources to mitigate the expenses accordingly. 

3. Faster time to Resolution with Lower Expenses

Prioritizing Scalability Testing will save money, fix bugs, and automates systems. Therefore, correcting errors in the testing phase is easier and cheaper than in the production phase. Fixing defects in a production phase cost more when compared to a testing phase. It improves the system by making it sustainable to handle the burst load and sudden increase in traffic with little or no notice.

Popular scalability testing tools

Scalability testing tools depend on the application the user wants to test. There are various tools available in the market, and a few tools are as follows:

  • LoadUI Pro

  • LoadNinja

  • Apache Jmeter

  • Load View

  • Neo Load

  • Load Impact

  • Blitz

  • Loader

Every Scalability testing tool has its unique features to test the Scalability of an application. However, every organization is bound by few environmental factors that are necessary for an application. Such factors can be affected while choosing a scalability testing tool to test a system. Testers need a reliable test tool to handle heavy load under various scenarios created.

Approaches of Scalability Testing

There are two approaches to Scalability testing –

1. Horizontal Scaling:

Physical machines and resources are involved in reducing the load on each device or resource. It consists in increasing the number of nodes instead of increasing the capacity; therefore, the load is distributed between the old and newly added resources.

Google, Yahoo, Facebook, Amazon, etc., perform the Horizontal Scaling because they have large projects/ applications running in a multi-node, distributed environment. They require a high level of computing and can be achieved using clustered, load-balancing, and distributed file systems. Theoretically, it is easier to perform horizontal scaling by adding the resources in the existing system, but practically, it is very tough to Scale-Out the application.

2. Vertical Scaling:

Vertical scaling increases the power of machines in CPU, RAM, Disk to the server. Vertical scaling can be like adding more CPUs to the same single server. With the increase in load, the system’s performance starts going downhill, but to maintain the efficiency of the system, vertical scaling is applied.

Vertical scaling is applied for small applications where the load’s performance can improve by increasing the capacity and size (scale) of already used resources. In vertical scaling, data is stored on a single node in one place, and the load is divided between several CPUs and memory through multi-node. 

Advantages and Disadvantages of Scalability Testing


Below provided are some of the advantages of Scalability testing:

  • Scalability testing determines the end-user experience under the specific load, and corrective measures are taken in advance to rectify any problems and make the application or system more scalable.

  • Response time, Network Usage, CPU Usage, etc., can be used to determine web applications’ web response and limitations.

  • Rigorous testing is conducted on a system before releasing it into the production environment to reduce the risk of a massive loss of money and the company’s reputation due to the bad performance of an application. 

  • Scalability testing helps uncover multiple defects during the testing phase. It is economical if detected in the testing environment rather than the production environment.

  • Effective tool utilization tracking happens when the testing is deployed.


  • The testing environment produces more defects due to various issues in a system. Therefore, the production environment is different from a testing environment.

  • Deploying advanced testing tools involves much more finances causing an over budget of the project.

  • Time spent on every test case increases with detailed testing procedures. Therefore, deploying a scalability testing process may sometimes cause a delay in meeting the project’s deadlines.

  • The wrong testing process can lead to failed test cases in the testing phase. The test scenarios and test scripts need to be changed, leading to a waste of time making unnecessary changes.

  • Defects cannot be detected in a narrow test window; therefore, critical defects remain undetected, resulting in project failure.

Final note

Scalability testing is desirable in software testing process because it helps avoid any issue or problem in daily business operations. It is a part of testing process in most software development teams in order to test how the application handles increase in user traffic, data volume, and transaction counts. It includes a separate team of professionals and testers who are resourceful with strong analytical skills. It differs from organization to organization and from application to application.

To sum it up, any application or infrastructure needs to be versatile enough to withstand the ever-growing dynamic requirements of the users. Implementing Scalability Testing helps in identifying fluctuations, upwards or downwards, performance metrics, or site degradation. Using Scalability Testing regularly helps in meeting business goals and smooth functioning. There are no shortcuts to ensure complete customer satisfaction and brand awareness while reducing any infrastructure costs at the same time. QAonCloud Scalability testing tools are flexible and robust enough; they perform the test most efficiently with solid reporting and analytics implementation.