Functional vs. Non-Functional Testing

 1. Introduction

In this article, we’ll explore the basics of testing. We’ll also explore some of the differences between functional and non-functional testing. Finally, we’ll discuss some of the types of both functional and non-functional testing.

2. Testing and Its Significance

Testing plays a significant role in the Software Development Lifecycle. It is essential to protect the software from defects, vulnerabilities, and malfunctioning, and to provide guaranteed quality assurance. Moreover, the bugs or errors, if any, should be identified early and fixed. Testing helps us do that.

We evaluate the software against the requirements and report the defects to make it reliable and robust. If the software doesn’t match the specified requirements, functional as well as non-functional, it’s of no use. Moreover, it must always efficiently handle all the exceptional and corner cases. Software testing is essential and unavoidable for delivering an efficient, accurate, and usable product.

3. Functional and Non-Functional Testing

Let’s understand the two important categories of testing: functional and non-functional testing.

In functional testing, we ensure that the functionality of the software meets the business requirements. We prepare tests to specifically focus on the functional requirements such as business use cases. This means we prepare a set of inputs and the expected outputs and test the system for accurate values. Thus, functional testing is a way to guarantee that the application is built to satisfy all the business use cases as expected.

We generally perform non-functional testing after functional testing. In non-functional testing, we focus on the evaluation of the non-functional aspects of the system such as performance, usability, reliability, and scalability. It ensures that the user gets the best experience while using the software. Non-functional tests are as important as functional tests since they help us understand how the system behaves under certain circumstances. Therefore, non-functional testing is a way to guarantee that the application is robust enough to handle unknown external factors.

4. Types of Functional Testing

Let’s understand the types of tests that fall under functional testing.

4.1. Unit Testing

Unit testing is the “white box” approach to testing the functionality of the code against the requirements. We write tests to check if the written code works correctly. As a result, we can cover the defects and report those at the earliest phase of the Software Development Lifecycle.

As soon as we develop a new feature, we can write the unit tests in parallel to check that the feature works as expected even in unexpected scenarios. Moreover, we should ensure that the unit tests cover the functional reliability of the product. Finally, we should ensure that we follow the best practices for writing unit tests in Java.

4.2. Integration Testing

Once all the components and modules are built, we can perform integration testing of those modules. Here, we test that the integration of all the individual components of a product work according to the business expectations. We verify that the individual modules and components work as efficiently after the integration as they do independently. Furthermore, we should ensure that the unit tests and integration tests are successfully evaluated before deployment.

4.3. Sanity Testing

We perform sanity testing once an upgraded version of the software is available after fixing a small issue in the functionality. We verify that the developers have fixed all the reported defects and there are no further issues because of the new changes. Therefore, this type of testing specifically focuses on the parts of the software being changed.

4.4. Regression Testing

We perform regression testing if a new feature is introduced in the software or if some code changes are done. The untouched features of the software must function the same as before even after the code changes or improvements. Thus, we re-test the functionality of the software to ensure that existing features still work as intended.

4.5. Smoke Testing

In smoke testing, we verify that the software build is stable and ready to perform the next rounds of testing. Sometimes, we call this build verification testing.

4.6. User Acceptance Testing (UAT)

UAT is the last step of testing that we perform before the release of the software. Generally, the end users perform this testing to ensure the software works just as expected.

4.7. System Testing

Once the entire product is built, we perform testing of the end-to-end product that may comprise both hardware and software testing. All the tests are run on the fully integrated product along with the peripherals to test how these components interact with each other. Additionally, we verify all the desired outputs for a specific set of inputs.

5. Types of Non-Functional Testing

Now, let’s also understand the types of tests that fall under non-functional testing.

5.1. Performance Testing

An application may crash if we load it with a huge number of requests at once. We do performance testing to ensure that the application remains stable and responsive under the given workload. This testing helps find performance bottlenecks, hence we essentially focus on the speed, stability, and scalability of the software. Thus, we need to verify that the application responds quickly, remains stable, and all the services remain available under the maximum user load.

Endurance testing, load testing, stress testing, spike testing, compatibility testing, volume testing, and scalability testing all fall under the performance testing umbrella.

5.2. Security Testing

Security Testing is an essential part of software testing to ensure that there are no vulnerabilities, threats, or risks in a software application. We run security tests to reveal flaws and loopholes in the security mechanisms of the system. This is necessary to protect the system against malicious attacks from intruders.

Network security, data security, authentication and authorization, client-side and server-side security, denial of service, and URL manipulation are a few of the focus areas of security testing.

Ethical hacking, Security Auditing, Security Scanning, Vulnerability Scanning, Risk Assessment, Posture Assessment, and Penetration testing fall under security testing.

5.3. Usability Testing

In usability testing, a certain designated set of users perform typical tasks using the software to evaluate a product. They focus on how easy a software application is to use in order to meet its objectives. Therefore, we also call it User Experience (UX) testing. It helps improve end-user satisfaction.

Some of the most important criteria for usability testing are:

• Accessibility and ease of use
• Efficiency
• Desirability
• Accuracy
• The usefulness of the system

5.4. Localization Testing

Localization testing focuses on the behavior of the system for a specific geography or locale. We customize an application for a targeted language or country. Thus, we check if the language, messages, date and time format, notifications, and more, are designed according to the targeted region.

We specifically focus on the contents and UI to perform localization testing. Based on the regions, we may change the initial settings and user interface according to the requirements. Hence, for doing localization testing, we need expertise in the domain as well as in i18n engineering.

6. Conclusion

In this article, we learned the purpose of functional and non-functional testing and compared the two. We also learned various types of functional and non-functional testing. Lastly, we explored when to use the various types of functional and non-functional testing techniques.