Introduction: 

When it comes to software testing, one of the important distinctions should be made in the non-functional testing vs functional testing since both are critical in creating high-quality and better performing products. Even though functional vs non-functional testing in software testing may appear to be very alike, they differ in various aspects because they serve entirely different purposes in the scheme of software testing. Together with that, here, in this blog, we are going to discuss “ what is functional and non-functional testing”  and contrast both, outline the goals for each, and explain how all of that helps to build reliable and high-quality software.

For better understanding of the difference between functional and non-functional testing, we will discuss each separately first.

What is Functional Testing?

This is a subcategory of software testing that checks whether the specific software performs as it is required to perform. It answers the question: What is the core of the software?

Functional testing involves comparing the existing versions of the software against the intended results, to ensure that every feature and function operates as planned. Functional testing deals with the user requirements and it tries to validate whether the software is capable of performing the work it is expected to do. It is based on the principle of functional vs non-functional testing in software testing where the focus is made to meet the user requirements.

Types of Functional Testing:

Unit Testing

Unit testing involves testing individual components of an application to ensure they function correctly. For instance, in an API application, unit tests may make requests to the system in a testing environment and compare the responses with the documentation. However, unit tests have limitations. They primarily focus on isolated parts of the application. Application-wide functional tests are often needed to detect changes or regressions that unit tests might miss.

Integration Testing

Integration testing checks how well different software modules work together. When code is written as loosely-coupled modules—an ideal approach—the components depend on clear contracts defining their interactions. Integration tests confirm that each module adheres to its contract and flag any regressions introduced by changes in these interactions.

User Acceptance Testing (UAT)

During the user acceptance phase, developers provide the application—either partially or in full—to end users or their representatives. This phase models real-world interactions and functionality. Although some engineering cultures minimize reliance on UAT due to its cost and time demands, it remains a crucial part of testing for many applications.

Closed-Box Testing

Closed-box testing, also known as black-box testing, examines the application’s outputs without considering its internal workings. This approach is useful for functional testing, particularly when complemented by non-functional tests. In cases where only API interactions are involved, closed-box testing is straightforward: the code makes API calls and evaluates the results. For applications with a user interface, this testing becomes more complex. Tools like Selenium can automate this process by interacting with the application as a user would in a web browser, though it can be resource-intensive and complex.

Smoke Testing

Smoke testing is performed before detailed system testing to ensure that critical functionalities are working properly. This preliminary check helps avoid the need for reinstallation and further testing if key functionalities fail, thereby saving time and resources. Smoke testing provides a broad overview of the application’s health.

Sanity Testing

Sanity testing focuses on specific functionalities or fixes that have been applied to ensure they work correctly. It is more targeted compared to smoke testing, addressing particular changes or bug fixes to confirm that these updates haven’t introduced new issues in related components.

Regression Testing

Regression testing is conducted after receiving a new build of the software following bug fixes. It verifies that the reported issues have been resolved and checks that the software continues to function correctly across all features with the applied changes. This type of testing ensures that recent fixes haven’t negatively affected other parts of the software.

What is Non-Functional Testing?

Non-functional testing targets the ways the software interacts in contrast to non-functional testing which targets the content of the software. This kind of testing is performed on aspects of software quality which include its performance, reliability, usability and other properties. Non Functional testing determines the level of quality of the attributes like, Performance, security, usability and scalability that the software product comes with.

This focus is important to realize the entire spectrum of functional testing vs non-functional testing kinds. So, it is crucial to distinguish between the two types of testing, being non-functional testing vs functional testing differences, the latter of which guarantees that the software works not only effectively but also in a range of conditions.

Types of Non-Functional Testing:

Performance Testing

Performance testing is a crucial aspect of non-functional testing, focusing on how well a software system responds to requests. It measures whether the system can handle requests promptly and efficiently. Poor performance can significantly impact user experience, so effective performance tests are designed to identify and address issues before they affect users.

Load Testing

Load testing is non functional testing, which involves testing of the system under different loads. It tests the capacity of the system to support load such as 10, 000 requests for one second and check on the performance of the system during peak traffic. It also validates that the system is capable of handling load and, in case, it is unable to do so, it will show how it handles graceful failure and helps to determine the system’s scalability and utilization.

Usability Testing

Usability testing analyzes the issue of quality with the aim of determining how easy or complex it is to use the software. Normally a completely manual activity, usability testing can be very hard to go large as a scale. Although, it is useful in pinpointing activities that could culminate in the emergence of confusing or unpredictable interfaces. More time spent on usability testing would highly improve the applications hence making usability testing especially when is being done while localizing applications valuable.

Security Testing

As mentioned earlier security testing guarantees that software applications are both secure and manage data correctly. Such testing could be as simple as scanning the application for vulnerabilities, to as comprehensive as penetration testing, depending on the openness of the application to such testing. Quite often, security testing might be disregarded, yet, it should become as inalienable a part of the testing process as unit testing in order to ensure that the application under test is invulnerable to certain breaches.

These are the various functional testing vs non-functional testing types for you to better understand.

Functional vs Non-Functional Testing Comparison:

Understanding “What is functional and non-functional testing?”  is essential for developing a comprehensive software testing strategy that ensures both functionality and quality.

Here’s a table summarizing the differences between Functional Testing and Non-Functional Testing in software testing: