Functional and Nonfunctional Testing Explained

Feb 28, 2023 | Test Automation Insights

people working in a computer lab

Software testing is an indispensable practice in software engineering and development, helping businesses deliver high-quality and error-free digital products. However, software testing is an umbrella term that includes various methodologies and approaches.

When implementing a testing strategy, one of the key distinctions is whether the testing should be functional or nonfunctional — or both. What are functional and nonfunctional testing? In this article, we’ll discuss the differences, similarities, and advantages of both testing methodologies, helping you determine which variety better suits the scope and trajectory of your software project.

What Is Functional Testing?

Functional testing is a type of software testing that’s designed to assess the quality of the software’s functional capabilities and behavior. The goal is to ensure that the system can effectively do what the functional specifications say it’s capable of doing. Any failed parameters are then highlighted as deficiencies that require fixing.

Functional testing focuses on the active implementation of the software and how it’s expected to react based on the behavior and activity of the users. It’s conducted as a type of black-box testing, where the software is fed input for the testers to examine and analyze the output. In this scenario, the internal structure of the program is rarely considered.

How It Works and Functional Specifications

Functional testing is one of the most important techniques when assessing a software’s functionality. For a comprehensive and successful test, it needs to include a variety of features, the user interface, databases, and a number of the software application’s special functional specifications.

Testers can conduct functional testing through either manual or automated means. This is mainly determined by the scope and complexity of the piece of software in question. In any case, the testing can help add to the official documentation used to describe the digital product’s functionality, capabilities, and overall user interface and appearance.

Smoke Testing vs. Sanity Testing

While serving similar goals in ensuring the functionality of a piece of software, smoke testing and sanity testing approach the matter from different angles.

Smoke testing is used to extract a high-level overview and understanding of the software’s critical functionality. It allows the team’s developers and testers to immediately identify any major issues at hand.

On the other hand, sanity testing is conducted randomly on a more stable version of the software, and it’s usually considered surface-level testing. It’s quick and basic but just as critical for ensuring that the changes implemented during smoke testing are working properly with no bugs.

By utilizing both types of functional testing, software testers are able to effectively identify critical issues within the system that require further investigation while also verifying the high standards of the software.

Integration Testing

Integration testing is another essential functionality testing method. It examines the quality and reliability of interactions between various application modules.

Using integration testing, you’ll be able to ensure that individual units, components, and modules of the application are all working as intended and can properly communicate with one another. This type of testing is best used in identifying integration problems, especially at the early stages of development, making them considerably easier and less costly to resolve.

Regression Testing

Regression testing sits on the very edge between functional and nonfunctional testing. It seeks to identify issues and contradictions that may have been caused by changes to the application’s code during the later stages of development.

It’s the process of rerunning all the functional and nonfunctional tests the software was put through to ensure all the previous issues have been resolved before the official release of the software product. 

What Are the Benefits of Functional Testing?

Testing the functionality of a piece of software before its initial release to users is a critical step. There are several benefits that emerge from adequately implementing functional testing into your software testing strategy, such as:

  • Improving the efficiency and productivity of developers
  • Reducing fatigue associated with manual functionality testing
  • Improving application quality
  • Saving time and costs for businesses in the long run

What Is Nonfunctional Testing?

Nonfunctional testing is a type of software testing that evaluates the nonfunctional aspects and components of an application. It focuses on how the system operates and whether it meets specific user requirements rather than its more technical and functional aspects.

Primarily, it deals with evaluating the software’s performance, scalability, security, overall usability, and dependability. Through a nonfunctional testing strategy, you can identify blocks and hurdles that users might have otherwise encountered, negatively affecting their experience.

Through nonfunctional testing, software testers are able to detect and remove faults or defects in an application before it causes a problem for its users.

How It Works and Nonfunctional Requirements

Nonfunctional testing is just as essential as functional testing in producing high-quality software. It’s conducted mostly during the later stages in the development process, ensuring all the software’s nonfunctional parameters, such as stability, security, and performance, are up to standard.

You can conduct the tests either manually or through automated testing tools, depending on the scope and complexity of the software in question. It covers various aspects, ranging from maintenance and documentation accuracy testing to the user experience.

Load Testing

Load testing is one of many nonfunctional testing approaches. It’s used to evaluate the performance of an application when subjected to varying intensities of loads and conditions.

At its core, load testing involves the simulation of a large number of simultaneous users to test the application’s performance boundaries, irrespective of its functional capabilities. Instead, it focuses on parameters such as response time, resource utilization, system stability, and throughput rate.

Performed properly, load testing can help developers identify any weak points within the structure of the software and work on solving them accordingly.

Stress Testing

Stress testing allows developers to measure the impact of intense workloads and other challenging scenarios on the software’s performance. Analyzing and understanding how a program responds to extreme stress offers valuable insights into its overall performance and resiliency.

By comparing the results of the tests to the anticipated everyday user activity, developers can gauge the software’s capacity and prepare for it accordingly.

Security Testing

Security testing is another type of testing that sits at the intersection between functional and nonfunctional testing. It aims to ensure that the application is free of all potential vulnerabilities, risks, or weaknesses that may pose harm to the users’ data security and privacy.

Also, security testing may be mandatory depending on the region where the digital product is going to be deployed. Performing such testing verifies that the software is up to standard.

The development team can catch and address any security vulnerabilities the test catches before they can cause an issue for users, most notably data breaches and denial-of-service attacks.

What Are the Benefits of Nonfunctional Testing?

Testing the performance and general capabilities of an application prior to the release of the software is essential to ensuring an elevated user experience.

There are a number of benefits that result from the proper implementation of nonfunctional testing capabilities, such as:

  • Creating a more resilient and reliable software
  • Reducing the risk of security issues
  • Improving the user experience
  • Reducing business risks associated with poor performance and security issues
  • Improving system performance and scalability

Key Differences Between Functional and Nonfunctional Testing

The functional and nonfunctional requirements of a piece of software should both meet base standards set either by a governing body or by the business itself. However, just because both testing types are essential doesn’t mean they’re the same.

So, functional versus nonfunctional testing — how do they measure up against one another?

Functional testing takes a thorough approach to verifying the quality and lack of bugs and issues within the software’s individual technical and functional components. Those can range from a few features to hundreds of different components, depending on the scope of the software project.

It combs through the code in search of bugs and inconsistencies that may negatively affect the functionality of an implemented feature, the user interface, or connection and access to the database.

Nonfunctional testing, on the other hand, is more concerned with the user experience than the technical aspects of the software. However, it’s just as necessary in completing the picture to evaluate a piece of software before it’s released to its intended user base.

Although there are many types of functional and nonfunctional testing approaches and methodologies, they aren’t always all used or used to the same extent. By creating a comprehensive testing strategy alongside quality assurance professionals and customer support, software testers and developers can plan the best course of action when it comes to testing.

Use Test Automation Software to Streamline Your Projects

Test automation can be an invaluable tool for organizations looking to scale testing or perform continuous testing on a large and complex piece of software. It enables you to run functional and nonfunctional testing with increased speed and accuracy, all while reducing the rate of human error and stress put on developers.

Ranorex’s automation software, Ranorex Studio, is our flagship product, used by QA teams and software developers during functional and nonfunctional testing of their digital products.

Try our automated software testing tool with an instant demo today.

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