robustness testing

What is Robustness Testing in Software Testing?

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Delivering high-quality, reliable software products requires rigorous and various levels of software testing. It becomes essential for quality assurance (QA) professionals and testers to perform multiple checks on software products to ensure they meet all functional and non-functional requirements. 

When users utilize software after its launch, it is obvious that they input invalid or unexpected values. The software should function correctly and withstand any unexpected and invalid values in such cases. This is where robustness testing comes into play. 

It is a quality assurance methodology or testing type concerned with validating the robustness of software products. In other words, this testing type verifies software products for their reliability and consistent functioning even under unexpected inputs and stressful conditions. It determines the degree to which software products can function correctly under stressful conditions. 

Continue reading this article to learn more about robustness testing and its various aspects. But before that, let us briefly introduce the term ‘robustness’

What is Robustness in Software Testing?

Robustness in software testing is a metric that defines how well a software product can handle invalid inputs and unexpected or stressful conditions. A robust system can adapt to different environments quickly and continues to function correctly or as expected. In addition, it handles any errors and unexpected events without getting crashed or producing incorrect outputs. 

For example, consider you developed software and deployed it on Ubuntu. Your team eventually decides to deploy it on Windows Virtual Machine. If your software is robust, it would quickly adapt to a different operating system than the one on which it was deployed, and that too with minimal code changes. 

Robustness is of the utmost importance for safety- and mission-critical software products. It is also important for systems whose failure may have serious consequences.

What is Robustness Testing?

It is a type of non-functional software testing that aims to verify the functioning of a software product or component under various unexpected conditions, invalid inputs, or when it operates outside its intended operating environment. It uncovers memory leaks and all other types of errors that would lead the software system to crash under unexpected events. 

Hence, we also sometimes refer to this testing type as Endurance, Stress, or Reliability testing. 

When performing robustness testing, quality assurance (QA) professionals primarily look for scenarios that can lead to the failure of the software product. They provide valid and invalid inputs and check the software’s reliability and functionality. In addition, they subject the system to different stressful conditions, such as stress, temperatures, high pressure, etc., and verify its functionality. 

To make it easy for you to understand, here is one simple example. Consider you develop a small program that takes input ranging from only 1 to 10. When you test the program for robustness, you provide inputs out of range, such as 0, -2, 11, etc. Even if you provide an invalid input, your program must respond as ‘Invalid Input’ rather than behaving unexpectedly.

Features of Robustness Testing

Here are the worth-noticing features of robustness testing:

  • It is black-box testing, where QA professionals have no knowledge about the system’s internal working and implementation details.
  • It involves validating the system with a wide range of invalid, unexpected, or out-of-range inputs. 
  • QA professionals validate the system’s ability to handle unexpected errors and exceptions without crashing or failing.  
  • Robustness testing is usually done at the later stages of the software development life cycle (SDLC), after verifying that the software works well under normal conditions. 
  • It also verifies the system’s behavior under stress, such as high traffic volume and sudden increase in user requests. The system should be stable and perform consistently in such scenarios.

Why is Robustness Testing Important? 

The primary reason for performing this type of testing on software products is to ensure their safety and reliability.  

  • Identify Unexpected Errors: It will help you to identify the potential issues that can lead the system to fail or crash unexpectedly. The development team can fix those errors early before releasing the system/product to real users. This ultimately prevents system crashes or failure after production.

  • Stability: Robustness testing increases the stability of your system in extreme conditions, as it prevents system crashes and failures. Also, it ensures that the system can withstand invalid and unexpected inputs.

  • Customer Satisfaction: Customers are more likely to satisfy with their experience using your system if they see that your product can handle extreme cases. This can lead to increased customer loyalty and trustworthy relationship.

  • Reduced Cost: Robustness testing uncovers potential bugs before releasing the software to real users. The cost of fixing bugs or eros after production is high. This also comes with reduced customer satisfaction and trust.  

Types of Testing to Ensure the Robustness of Test Suites

Different types of software testing help to ensure the robustness of test suites (a collection of test cases). They are as follows: 

  • Functional Testing

Functional testing is a software testing type that validates the software product for its functionality. It ensures the product works as expected and meets all the specified user requirements. It involves running the product’s source code through a series of tests that validates its different functions. 

Generally, testers perform functional testing using various techniques and methodologies to ensure the product works well in different scenarios and conditions.

  • Negative Testing

Negative testing involves providing incorrect and invalid inputs to the system to check its response. It helps determine errors and bugs associated with boundary conditions and error handling, potentially leading to data loss or security vulnerabilities. This means negative testing validates the system’s ability to handle error conditions and exceptions without crashing or providing incorrect results. 

  • Load Testing

Load testing is a type of performance testing that checks how well your system performs under heavy loads and stress, such as a sudden increase in user requests. It aims to remove all performance bottlenecks and ensure the system’s smooth functioning. In addition, it helps determine the system’s maximum capacity to handle the load. 

  • Security Testing

The security of confidential data is paramount for every user or customer. Hence, the system should be able to protect user data, assets, and functionalities from unauthorized users and third parties. This is where security testing comes into the picture. It uncovers all security vulnerabilities, risks, and threats in the system that intruders or hackers could exploit.

  • Regression Testing

This type of testing ensures that any recent changes in the source code do not affect the system’s existing functionality. It ensures that the introduction of any new features or the modification of the source code does not have any impact on the existing features. The old code functions as it is, along with the new code. 

  • Stress Testing 

A type of performance testing, stress testing also involves deliberately putting the system through heavy loads. It is non-functional testing that determines the system’s ability to handle heavy loads, for instance, a huge number of user requests, while maintaining its functionality and performance intact. 

The primary aim is to check the system’s behavior beyond its capacity to handle the load. This helps testers determine the system’s breaking point.

  • Fuzz Testing

Fuzz testing is also a type of software testing that involves providing random input to the system to uncover exceptions, such as crashes, memory leaks, etc. It uncovers errors and potential security vulnerabilities. Its primary goal is to determine the input that makes the system behave unexpectedly.

  • Usability Testing

Also known as user experience (UX) testing, usability testing involves validating the software for user-friendliness, i.e., how much the software is easy for users to use. A small group of real users perform this testing and provide all feedback before making the software live to a large group of users.

  • Fault Injection Testing 

It is a testing technique that validates the resilience of software products. As the name suggests, it involves introducing faults into the system intentionally to determine its behavior and potential weaknesses.

Robustness Testing Tools

You can use several popular testing tools available on the market for robustness testing. They are as follows: 

  • Fuzz Testing tools: Tools like American Fuzzy Lop, AFL, Peach, and SPIKE, automate the process of providing random input to the system and identifying which input caused errors.

  • Selenium: It is an automated testing framework for web applications. It simulates user input and behavior to check the system’s ability to handle unexpected events and errors. 

  • Spock: It is a  Groovy-based testing framework to test Java applications. Its syntax is very structured and concise, helping developers test with convenience and ease. 

  • JMeter: It is another open-source performance testing tool that validates the behavior of web applications under extreme loads. It simulates a large number of users and requests to validate an application’s ability to handle high traffic. 

  • LoadRunner: It is another performance testing tool to check the behavior of web applications under high load.

Advantages and Disadvantages of Robustness Testing

Let us now shed light on the advantages and disadvantages of robustness testing. 


  • Improved Software Quality: When you put your software through robustness testing, it improves its reliability, durability, and ability to handle unexpected conditions and invalid inputs. It uncovers all potential errors that could lead to system crashes or failure.

  • Reduced Development Costs: This testing type identifies errors leading to system crashes and failure. If they are left unnoticed, you leave your software at great risk. Robustness testing eliminates the need to spend too much on software crashes or failures by identifying errors early before production. 

  • Uncovers Potential Security Vulnerabilities: By identifying security vulnerabilities, this testing type prevents potential online attacks and data breaches. 

  • Enhanced Customer Satisfaction: When the software works according to users’ expectations without any errors, they are more satisfied and likely to use it. 

  • Improved Competitiveness: You can gain a competitive edge by delivering high-quality, robust software products. 


  • May Not Uncover All Issues: There is no testing type that can uncover all issues, and robustness testing is no exception for that. It can uncover potential issues and security vulnerabilities but cannot discover all. 

  • Time-Consuming: If the software is complex and has multiple features, it takes a long time to test all features with multiple inputs. 

  • Requires Specialized Skills: Performing robustness testing requires a profound knowledge of software testing and the software product under testing. 

  • Expensive: The use of specialized tools or equipment can make this testing type more expensive. 


This was all about robustness testing. It is a type of software testing that validates a software product’s behavior, reliability, and consistency with invalid inputs and unexpected events or conditions. It is very critical to the software development life cycle, as it uncovers potential errors that could result in the software crash or failure. In addition, it discovers potential security vulnerabilities that intruders or hackers would exploit. 

We hope this article has provided you with an in-depth understanding of robustness testing.

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