Scalability Testing: A Simple Overview in 5 Points


The method of non-functional testing using the performance of a network or system during up/downscaling it is called scalability testing. It is used to test the system’s ability to deal with the scaling and projected decrease/increase in data, traffic, frequency of transaction counts, data volume etc. It is used in software engineering testing to check to which limit the application can scale and why it cannot scale further. It focuses on the application’s behavior when it is deployed to scale to excess loads or work as a larger system to compare scalability vs performance testing. Hence it is also called scalability in performance testing.

In this article let us look at:

  1. Scalability Testing
  2. Why do Scalability Testing?
  3. What to test?
  4. Test Strategy
  5. Scalability testing Vs Load testing

1. Scalability Testing

One develops a test plan in great detail to create and develop a detailed test plan for scalability testing in software testing. The test plan application requirements are critical to testing, and the features required to be conformed to are as follows.

  • Script Steps should define the user’s exact performed actions.
  • Run-Time Data required is to be determined for all the application’s data interactions.
  • Tests that are data-driven mean that if the scripts use varying run-time data, all fields of such data need to be defi0ned.

Scalability and performance testing includes the following steps. Firstly, one defines the repeatable scalability test process, which should last for the application’s entire lifecycle. Then one has to define the various scalability criteria, scalability testing tools and decide on the software required to run the loading tests. The environment is also to have the hardware and test scenarios required to execute scalability testing. The visual script created and the load-test simulation scenarios need to be verified after creation. Only after these are completed should one execute, evaluate and generate test reports of the scalability testing.

2. Why do Scalability Testing?

In all software applications, scalability testing is a critical factor for deployment. It is meant to determine how much the application can be scaled and when it stops scaling why it did so. Thus scalability testing allows one to determine up to what loads the application can be scaled. It is also used to determine web application loads or the limits placed on the user numbers. It is also used to determine the end-user experience and how much degradation happens on the client-server side. This allows one to also determine the degradation and robustness at the deployment server end of the scalability testing example.

3. What to test?

The scalability testing approach puts to test the following attributes of the software. Namely

  • The time taken for screen transition to occur. 
  • Response Time.
  • Throughput.
  • The per-second rates of transactions, requests and hits.
  • The time factors for rebooting, session times, transaction time, printing time, task execution times, etc. 
  • The number of users for performance measurement.
  • Memory/ CPU Usage
  • The usage factor of the network 
  • Load measurements for performance measurement testing.
  • Response and requests rate per second for the webserver.

4. Test Strategy

The Test Strategy depends on how to perform scalability testing, many parameters and the application under test. For example, if the application under testing uses a database, then the parameters of testing need to test the database size and the user numbers etc. what is important though that the testing strategy is very clearly spelt out before scalability testing is executed.

The prerequisites are

  • Memory– One will need to compute how much memory will be used by the load test master and the virtual user agent. 
  • Operating System- Checking on the load test master and load generation agent’s operating system is also critical. 
  • Capability for Load Distribution– One should check if the load test tool can be controlled from a central hub and whether it enables multiple machines to load the system.
  • Processors Used– This factor also needs to be checked both on the load test master and the virtual user agent CPU’s sides.

5. Scalability testing Vs Load testing

Scalability and load testing are different tests in the scalability vs load testing rundown. The scalability testing tests the system’s ability to deal with changes during scaling and measures performances in the volume and size of the system. On the other hand, load testing implies running the system under various heavy load conditions to check at which loads the system slows and response times are too large, implying system failure.


Scalability testing services use a special type of software testing that checks for the network/ system’s ability to scale up when the volume/size of the system is altered to meet the organization’s needs. The strategy behind scalability testing depends on the type of the application’s organizational use and focuses on when the system stops scaling and why it does so.

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