Functional and Non-Functional Testing

Published: 22 Nov 2022

Functional and Non Functional Testing – Overview, Key Differences, and Tools

Last Updated: 24 Nov 2022

Content 1. An Overview of Functional and Non Functional Testing 2. Role of Functional Testing 3. Role of Non Functional Testing 4. Different Types of Functional and Non Functional Testing 5. Functional and Non Functional Testing: Key Differences 6.Top Functional Testing Tools 7.Top Non Functional Testing Tools 8. Conclusion

An Overview of Functional and Non Functional Testing

Functional Testing and Non Functional Testing

There is no denying the fact that comprehensive quality assurance strategies feature Functional as well as Non Functional testing. Therefore, it is important for digital businesses to understand the difference between the two. While both processes are an essential part of the application’s QA process, they serve distinct purposes.

Functional testing verifies that the app’s functionalities work according to the requirements by identifying the areas where performance does not meet the desired results.

On the other hand, Non Functional testing helps identify the broader quality concerns in an app by verifying all the non functional aspects, such as usability, performance, compliance, etc.)

Role of Functional Testing

Role of Functional Testing

Functional testing checks the application’s functionality against the defined requirements or specificationsalong with validating the snippets of the underlying code.

Comparing the actual outputs against the desired results provide a clearer picture than testing individual modules in isolation. Interactions between modules are frequently the areas where errors occur.

The role of functional testing is critical in validating the quality and functionality of the application. It is through techniques of functional testing, the quality assurance teams are able to verify the software functionality based on the Software Requirements Specification (SRS) and ensures the system performs as per the user specifications.

Functional testing helps to ensure the application is ready for release and is free of bugs and errors. Functional testing does not depend on any assumptions about the structure of the system and focuses on delivering a high-quality product. Various kinds of functional testing  methods are used to test usability features, error conditions, ease of accessibility, as well as testing other important functions of the software.

Role of Non Functional Testing

Role of Non Functional Testing

Non Functional testing validates the app features that may not be critical to functionality but are responsible for ensuring a seamless end-user experience.

Something that fails a Non Functional test does not always cause an issue that users would notice, but it can indicate a problem in the system — especially at scale.

In case non-functional testing is not performed for an application, it is not possible to measure the application’s ability to handle massive traffic, especially when the application experiences peak load. In scenarios such as holiday seasons or other scenarios when the app faces higher than usual traffic, the application may become slower or even crash. In another scenario, if the application is not tested for vulnerabilities and security, then it is prone to face cyber-attacks and even lead to exploitation of sensitive customer data. Incidents like these not only lead to a poor performing application that users might abandon, but also hamper the business’s reputation.

It is evident that non-functional testing is as critical as functional testing for a successful application. Non functional testing ensures the application performs seamlessly, while establishing reliability. It ensures the application may be counted on even during extreme conditions as it has been tested to meet all kinds of business criteria. After performing non functional testing, it may be assured that the application will be compatible with multiple devices and OS, ensure a user-friendly and accessible interface, meet the performance and load criteria, and meet the host of other vital business parameters.

Different Types of Functional and Non Functional Testing

Different Types of Functional Testing and Non Functional Testing

Common Functional testing types:

Unit testing: It is the first software testing phase in the software development lifecycle (SDLC). Software testers perform this functional testing type by creating and running test scripts to ensure the small units of the app individually work as desired.

Component testing: This functional testing type is similar to unit testing. However, the critical difference is that testers perform and test each application object separately with/without isolation from other software elements during component testing.

Smoke testing: Smoke testing is performed after every build release. Smoke testing helps to ensure all the test environment aspects are operating successfully and the build is stable for further testing.

Sanity testing: Testers perform sanity testing after smoke testing, which ensures the code changes continue to perform meet as desired.

Integration testing: During Integration testing, individual modules of the app are merged and validated as a group to identify the bugs and errors.

Regression testing: This functional software testing method helps ensure the changes made to the code are not affecting the application’s already existing features or functionalities.

System testing: System testing is performed after integration testing and is used for validating the fully integrated application.

User acceptance testing (UAT): This is the final software testing phase, wherein end-users or clients take up the roles of test engineers to validate whether the developed application meets the requirements or not. UAT is an essential functional testing type performed before moving the application to production.

Common non functional testing types:

non functional testing types

Performance testing: This testing process evaluates the system’s overall performance and ensures the app meets the desired response time.

Load testing: Load testing evaluates whether the system’s performance is as expected under normal and maximum conditions. Load tests identify the peak operational capacity of the app, and detects the causes of performance bottlenecks that lead to app degradation.

Stress testing: This testing process helps evaluate the system’s performance when it is low on resources. Stress testing measures low memory or low disc space on clients/servers that reveal defects that cannot be found under normal conditions.

Security testing: Security testing ensures no loopholes that may lead to data loss or breach. One important non functional testing type, security testing, includes testing the app for authentication, authorization, integrity, and availability.

Volume testing: Volume testing evaluates the app’s behavior when a significant amount of data is to be processed and checks the extent to which the app is able to handle large amounts of data.

Usability testing: This method of Non Functional testing evaluates the system for human use. GUI testing ensures the output is correct, meaningful, and the same as expected per the predefined goals.

Scalability testing: The scalability tests measure the ability of an application to scale its non-functional characteristics when required. This may be in the form of load the app can support, transaction count per second, data volumes, and so on.

User Interface (UI)testing: UI testing evaluates the GUI and ensures the GUI is consistent and provides easy navigation for application use.

Compatibility testing: This non functional testing evaluates the application for compatibility with other hardware/software with minimum as well as maximum configurations.

Documentation testing: Documentation testing validates user guides, set-up instructions, readme files, release notes, etc.

Failover testing: Failover testing ensures that the system is capable enough to handle additional resources, such as servers, in case of a system failure.

Compliance testing: Compliance testing is done by running audits to verify if the standards defined by the industry or government are being followed, such as GDPR, HIPAA, W3C, etc.

Localization testing: Localization testing verifies the app’s availability across cultures and locales.

Functional and Non Functional Testing: Key Differences


Functional Testing

Non Functional Testing

1 Validates the app’s operations and actions Validates the app’s behavior
2 It is based on the requirements of end users It is based on the expectations of end users
3 Performed to enhance the app’s behavior Performed to enhance the app’s performance
4 Easy to execute manually Difficult to execute manually
5 Validates what the product does Validates how the product does
6 Based on the business requirement Based on the performance requirement
7 It is carried out manually, such as Black box testing It is ideal to test using automated tools, such as LoadRunner.

Top Functional Testing Tools

Top Functional Testing Tools

Top Non Functional Testing Tools

Top Non Functional Testing Tools


Functional testing and Non Functional testing are the critical types of software testing that play a major role in ensuring the delivery of a high-end product. By facilitating end-to-end functional testing in the software testing process, testers can evaluate what the process is up to and how the app will behave under any given circumstances. With Non Functional testing, testers are able to deal with the system’s performance and describe how it performs under any given circumstances. Both have their distinct benefits and must be leveraged to ensure the final product is error-free and delivers a great CX.

Leverage functional testing and non functional testing services from next-gen QA testing service providers to deliver applications that perfectly meets your customer requirements and business objectives.

As a Leading QA testing services provider, how can TestingXperts help businesses?

TestingXperts (Tx) is one of the 5 largest pure-play software testing services provider globally. Tx has been chosen as a trusted QA partner by Fortune clients and ensures superior testing outcomes for its global clientele. We have rich expertise in enabling end-to-end testing services for global clients across various industry domains like healthcare, telecom, BFSI, retail & eCommerce, etc.

Our range of QA testing services include:

Functional Testing: Tx has years of experience providing functional testing services for clients across domains. Our wide range of functional testing services includes automation, manual, regression, and mobile application testing. We have in-house mobile test labs with numerous mobile devices.

Non-Functional Testing: Tx provides a wide range of non-functional testing services such as performance and load testing, security testing, usability testing, and accessibility testing. We also have an in-house performance testing accelerator, ‘Tx-PEARS,’ which helps with all non-functional testing requirements, including continuous monitoring of your infrastructure in production as well as in lower environments.

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