What is Non-Functional Testing? [Definition, Types, and Tools]

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What is Non-Functional Testing? [Definition, Types, and Tools]

Sameeksha Medewar
Last updated on July 20, 2024

    Testing is an integral part of the software development life cycle (SDLC) which ensures the delivery of high-quality products. The ultimate purpose of testing is to guarantee that the final product is free of glitches, meets certain quality standards, and fits the specified requirements.

    There are various types of software testing available out there, which tests different aspects of a software product. The two broad categories of software testing are functional and non-functional testing. Functional testing validates the software product against functional requirements, while non-functional testing validates the system against non-functional requirements.

    But what are functional and non-functional requirements? Well, functional requirements are the requirements specified by end-users and stakeholders. To put it simply, functional requirements are the features that the end-users want in the software product. On the other hand, non-functional requirements are the quality constraints that the system should satisfy as per the project contract.

    So, to test whether the software product meets non-functional requirements, a team of professionals carries out a particular testing process called non-functional testing.

    In this article, we shall discuss what exactly non-functional testing is and its types.

    What is Non-Functional Testing?

    Non-functional testing is a type of software testing that validates the software system for non-functional attributes, such as reliability, performance, usability, and security. In other words, this type of testing checks the behavior of the system with respect to non-functional aspects.

    The primary purpose of this type of testing is to verify the readiness of the software product in accordance with non-functional parameters that functional testing would never address. One simple example of a non-functional test would be checking how many users can log in to a particular system simultaneously.

    Moreover, this type of testing is equally important as functional testing. The reason is that end-users always want a high-performance, secure, and scalable software product having rich functionalities.

    The team of skilled testers validates the system by considering the following major non-functional aspects:

    • How does the software product perform under normal conditions?
    • What will be the effect of multiple users logging in to the system at the same time?
    • Can the system handle stress?
    • How secure is the system?
    • Can the software product recover from disaster?
    • Can the system behave the same when installed on different operating systems?

    This list goes on, which includes all other aspects that contribute to the overall quality of the software product.


    The primary objectives of non-functional testing are as follows:

    • Enhance the software product's usability, performance, reliability, security, and maintainability.
    • Reduce the production risk and cost associated with non-functional aspects of the software product.
    • Optimize how the software product gets installed, set up, managed, and monitored.
    • Improve the knowledge of the product behavior.

    Why Non-Functional Testing?

    In software development, it is very important to keep customers satisfied. And software testing helps organizations meet all customers’ requirements and satisfy them. There is no secret that customers want the desired functionality in a particular software product, and hence, organizations make sure to meet those requirements through functional testing.

    However, if you validate the system only for its functionalities, there may be chances that the end-users may face issues with it in terms of performance, security, and other non-functional aspects. Such aspects are not associated with functional testing and can affect the user experience. Therefore, non-functional testing is indispensable.

    Non-Functional Parameters

    The following are the parameters that testing teams consider while performing non-functional testing on a system:

    • Security
    • Reliability
    • Availability
    • Usability
    • Survivability
    • Scalability
    • Efficiency
    • Interoperability
    • Portability
    • Reusability
    • Flexibility


    The following are the remarkable benefits of non-functional testing:

    • Security being the most fundamental aspect of any software product, this type of testing ensures that the system under development is secure.
    • It helps the testing team to ensure the system’s loading capability, i.e., to ensure that multiple users can log in to the system simultaneously.
    • It significantly improves the performance of the system.
    • Test cases related to non-functional aspects never change. Therefore, you need to write them only once.
    • It consumes less time than other software testing types.


    The major drawback of non-functional testing is that testers need to verify the non-functional aspects of the system every time it gets updated.

    Non-Functional Testing Types

    The following are some popular types of non-functional testing that testers carry out on the software product to ensure its quality:

    1. Security Testing

    This type of testing considers security as its testing parameter and checks how the system can protect itself against various deliberate and sudden attacks from internal and external sources. Also, it verifies that the system has no loopholes, which may lead to data breaches.

    2. Performance Testing

    Performance testing validates the software product to check how well its components function. It intends to find the defects or errors in the software design and architecture. Moreover, the team of testers measures response time, identify bottlenecks, and locate failure points in performance testing.

    3. Load Testing

    Load testing validates the software system for its loading capacity. Here, the testing team checks how many maximum users can work on the system simultaneously.

    4. Stress Testing

    Stress testing checks how the software product behaves under abnormal circumstances. By performing stress testing, testers determine the limit at which the software product breaks. Moreover, it helps them to analyze what the system will do after failure.

    5. Reliability Testing

    Reliability testing checks for the reliability of the system. In other words, this type of testing checks how the software product works in a particular environment for a specific time period. The system is reliable only if it produces the expected results every time in the given environment.

    6. Usability Testing

    Usability testing checks the degree of ease with which the end-users can learn, operate, and interact with the software product.

    7. Availability Testing

    Availability testing validates the software product for its availability. It checks to what extent the software product can continuously perform the specific tasks or functions without any failure. The primary purpose of this type of testing is to verify the efficiency of the product beyond the standard operational capacity.

    8. Recovery Testing

    Recovery testing checks how the system continues to function and recover itself from failure. In other terms, it checks the ability of the software product to recover from various types of failures, including hardware/software crashes, network failures, etc.

    9. Scalability Testing

    Scalability testing checks the software product’s efficiency when the number of user requests gets scaled up or down. The major goal of scalability testing is to ensure that the software product can manage the increase in data volume, traffic, etc.

    10. Volume Testing

    Volume testing helps determine how the system behaves when a large volume of data is added to the database. Primarily, it identifies the behavior of the system when the data volume increases. Volume testing is also known as flood testing. Besides the aforementioned non-functional testing types, there are many others, such as compatibility testing, accountability testing, portability testing, maintainability testing, and documentation testing.

    Top 5 Non-Functional Testing Tools

    Since we have various types of non-functional testing, a lot of tools for each type are available in the market. The following are some popular tools for performance, load, and stress testing:

    1. JMeter

    JMeter or Apache JMeter is an open-source load and performance testing tool. Originally, this tool was intended to test web applications, but later, it expanded its scope to test other applications, servers, protocols, and web services.  Moreover, it comes with a fully-featured test IDE that allows you to build and record the test plan.

    2. LoadRunner

    Like JMeter, LoadRunner is also a performance and load testing tool to identify the system’s abnormal behavior quickly. It supports performance testing for a wide range of protocols and over 50 technologies and application environments. In addition, it helps you to quickly identify the causes of the performance issues with its patented auto-correlation engine.

    This tool comes with an IDE that can seamlessly integrate with development environments. Additionally. the LoadRunner Professional Engine enables testers to run unit tests.

    3. NeoLoad

    NeoLoad is yet another powerful performance testing tool for large enterprises. It is capable of carrying out performance testing on various types of APIs, applications, and other technologies. Basically, Neoload works by simulating the network traffic to examine the performance of the system under load. Also, it analyzes the response of the system when more users operate the system simultaneously.

    4. Loadster

    Loadster is a stress, performance, and load testing tool. This tool comes with a cutting-edge cloud hybrid load testing technique. This technique enables organizations to test large and complex applications and high-performance websites.

    There is no need to install this application since it can run directly in a browser. Moreover, it helps you record your test scripts, tweak or edit them, and run them right from the browser. It automatically generates test reports in the form of charts or tables after every test.

    5. LoadStorm

    LoadStorm is an on-demand stress, performance, and load testing tool for websites and web applications. Its major objective is to ease testing while being inexpensive. This tool generates test reports in the form of graphs that represent the response time, throughput, requests per second, error rates, and many other performance parameters.


    Non-functional testing is equally important as functional testing because it tests non-functional aspects of the software product that functional testing would never address. Before performing this type of testing, it is important to devise an effective testing strategy.

    All the non-functional parameters, such as performance, stress, load, maintainability, compatibility, security, efficiency, and many others, play a vital role in enhancing the user experience. Therefore, testing these parameters before the software product goes live is indispensable.

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    API testing is a type of software testing that validates application program interfaces (APIs) for their functionality, security, performance, and reliability.

    Non-functional requirements are the requirements associated with the quality of the software system. Non-functional requirements include security, performance, flexibility, maintainability, interoperability, scalability, reliability, efficiency, and compatibility.

    Functional and non-functional testing differs based on what they test. Functional testing validates the software product for its functionality, while non-functional testing checks different types of non-functional aspects of the system.

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