Stability Testing in Software Testing

There are many occasions where websites/applications have to run continuously for weeks/months without restarting the server. Since the number of users in such websites is exceedingly high, owners must ensure that users can access the website without facing any issues.

The testers' role in such situations is to make sure these websites don't face any failure or memory leakage when exposed to high traffic. Under stability test, testers revealed these websites till their breakpoint and check how the system responds to such load. 

Systems can crash or slows down under heavy load. It can also act erratically in some cases. Therefore, stability tests are usually performed before releasing the software or website to the end-users. 

What is Stability Testing?

Stability testing is a testing procedure that determines the software or website's ability to perform under a specific condition and timeframe. It is a part of non-functional testing, also known as Endurance testing.

The testing confirms that software possesses all the ability to perform well without unexpected failures, memory leaks, server restart under load, and other factors adversely affecting product stability.

Possible stability errors

  • System slow down
  • System becomes dysfunctional
  • Complete system crash
  • System acts weird


Let's say you purchased a smartphone or any other product from the market. Now, as a buyer, you expect your phone to work seamlessly for as long as you use it. Like most users, you may open Facebook, play games, and do multiple tasks simultaneously. A good smartphone must allow you to do all these tasks at ease. The last thing you want is that your phone stops working while you are in the middle of something.

Similarly, you don't want a website to stop working while you are in the middle of buying something online. Performance degradation in software or website can result in a significant setback for both developers and stakeholders.

The stability testing team's role is to identify such issues and report them to the development department for proactive measures.

During stability testing, following errors may surface −

  • the system slows down
  • the system encounters functionality problems
  • the system shows weird behavior
  • the system crashes altogether

In software development, stability and reliability could be confused, but they are different.

Why is Stability Testing Important?

The primary reason behind conducting stability testing in software testing is to know how the software or website will perform in real-time. It is crucial for developers as it allows them to understand the limitation of a software product. Besides, it gives them enough time to work on improvement before launching it.

  • Provide 100 percent assurance that the app/website is going to remain stable under high load

  • Allows developers to prepare adequate measures for any future issues

  • Ensure that the developed app/website can withstand a large number of users

  • Enable developers to detect memory loopholes and system errors

  • Facilitate adequate data for developers to compare the load coverage in stressful and normal conditions

7 Steps of Stability Testing

Step 1 − Ascertain the test coverage and goals, ensuring the app servers will not work efficiently while the load testing lasts.

Step 2 − The second step involves establishing the operational issues. Testers must confirm the system's reliability and load performance as per specific requirements.

Step 3 − Now the testers must allocate resources to execute the tests and functions. It involves drafting a thorough testing strategy, planning, execution, and monitoring.

Step 4 − It involves accumulating all the deliverables required for the testing.

Step 5 − Testers must ensure they have the right skills and tools to execute the process.

Step 6 − It contains a plan to analyze the threats and expenses involved in the stability testing process. The testers must estimate the correct execution costs considering factors like memory and CPU usage.

Step 7 − It involves steps to evaluate errors and align the system with the predetermined specifications.

Reporting Stability Testing

Under stability testing, testers collect a wide variety of metrics and report them to the development team.

Metrics collected in Stability testing includes −

  • Transaction response duration −Ascertain the time and course it takes for server requests to reach the app server.

  • Hits per second −Number of hits on the server by users.

  • Throughput −Calculates the total information a server receives at a particular timeframe.

  • Transaction per second −Determines the total transactions executed during the testing.

  • CPU, Memory, and Disk −Evaluates CPU % used, memory expended, and disk are used while testing.


1. What is the difference between reliability and stability testing?

Reliability in Testing − Reliability is a process that includes testing or measuring a software product's ability, ensuring it offers the same results when tested repeatedly.

Example of Reliability − Let's consider installing a new app on your mobile phone, but the application crashes every 5 minutes of usage. The good part is you don't lose your data after relaunching the app. Meaning, the app doesn't lose its reliability, even though it's not stable.

Meanwhile, let's say your newly installed app doesn't crash but fails to save your data correctly. You can consider this app as 'stable' but not 'reliable.'

Stability testing − On the other hand, stability is a time-varying process to study the performance of a power system under specific conditions. A software product is assigned to repeated tests at a specified date to determine its stability. The results of all the future tests are then compared and correlated with the initial tests.

Example of stability testing − Every time you purchase a mobile phone, you become a part of stability testing. Once you set up your new phone, you start storing images, videos, and other data in device memory to the point that it makes the phone runs slow. Then you start removing old data so that the phone again starts to perform like its old self.

2. What are some tools for stability testing in software testing?

Here are some of the most popular stability testing tools available in the market

  • WebLOAD
  • Apache JMeter
  • CloudTest
  • Httperf
  • LoadImpact
  • LoadRunner
  • WAPT
  • Performance Tester
  • Testing Anywhere


Stability testing is a crucial non-function testing technique that helps a software or website achieve full performance in harsh conditions. It prepares the system to tolerate critical load and stress, leading to a better user experience and a better life of the software product.

Updated on: 27-Apr-2021


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