What’s the Difference Between Functional and Non-Functional Testing?

Functional and Non-Functional Testing

What’s the Difference Between Functional and Non-Functional Testing?

Functional and Non-Functional Testing are two fundamental aspects of software quality assurance, each serving a distinct purpose in ensuring the reliability and performance of software applications.

Functional Testing:

Functional testing primarily focuses on evaluating the functions and features of a software application to ensure that it performs as intended. Testers examine the application against predefined requirements, and the key objective is to verify that it delivers the expected outcomes under various conditions. Test cases are designed to check specific functionalities, such as user interactions, data processing, and output generation. The goal is to identify any functional defects or discrepancies between the actual and expected results. Functional testing is essential for confirming that the software meets its intended purpose and user requirements.

Non-Functional Testing:

Non-functional testing, on the other hand, assesses aspects of an application that go beyond its basic functionality. It is concerned with performance, reliability, usability, and other quality attributes. Non-functional testing includes various types, such as:

  • Performance Testing: This evaluates how well the application performs under different conditions, including load testing, stress testing, and scalability testing.

  • Usability Testing: It examines the user-friendliness of the software, focusing on the user experience, accessibility, and overall usability.

  • Security Testing: Security testing identifies vulnerabilities and ensures that data and resources are adequately protected.

  • Reliability Testing: This verifies that the application consistently operates without failures or crashes.

  • Scalability Testing: It assesses how well the software can adapt and handle increased workloads.

In summary, while functional testing ensures that the software functions correctly, non-functional testing validates its performance, security, and usability under diverse conditions. Both types of testing are crucial for delivering a well-rounded, high-quality software product that meets user expectations and performs reliably in real-world scenarios.

A well-designed Quality Assurance strategy should cover all software aspects. It would not only check the basic functionality of the application but also the way it performs its required functions.

By understanding the difference between the two objectives, we establish that quality assurance agendas need to be distinctively dedicated to testing both how the application behaves (Functional Testing), and at what level of performance (Non-Functional Testing).

In this article, we will learn the definition of both main testing approaches look at their key differences, and how we at Q-Pros apply each testing type to our services.

What is Functional Testing?

what is Functional-Testing?

Functional testing is mainly concerned with testing a software’s behavior under test. This means we build a set of test cases, and we examine if the software is responding with the expected output. These tests are done in real environments to guarantee that the actual result is synchronized with client demands. This type of testing mostly consists of Black-box testing and is unconcerned with the application’s source code.

Types of Functional Testing:

Smoke testing – This type of testing checks functionally on a crucial level (Making sure the applications are working fine), it paves the way for other testing types to take part.

Sanity testing – It is regarded as an extremely specific way of testing; it mainly focuses on testing a specific function within the application to check if it runs properly with no bugs or defects.

Integration testing – This type of testing will determine if components within the system that are intended to integrate are functioning correctly in one singularity.

Localization testing – A technique in which tests are performed to check if the application can cope and be suitable with local changes i.e., language, region, time zone. etc.

Regression testing – A testing method that proceeds any changes that occur to the system’s internal code to make sure no new bugs arise as a result of the modification. It also checks to see if the entire system is working fine with the novel changes.

User Acceptance Testing (UAT) – This testing method is used to make sure that the application meets the user’s standards. Under a certain set of criteria, UAT sessions are carried out before the official launch/release date, to make sure that the applications hold their ground within a real environment and guarantee “user’s acceptance.”

What is Non-Functional Testing?

what is Non-Functional-Testing?

Non-functional testing is the testing of software application for its non-functional requirements i.e., the way the system operates, rather than the way the system behaves

Non-functional testing is designed to assess a system’s readiness using non-functional factors never addressed by functional testing. Checking how many individuals can simultaneously log into software is an example of a non-functional test. Non-functional tests are just as important as functional testing and impact customer satisfaction.

To consider any application a reliable one, we must check if the application is running smoothly with speed and efficiency, this will assure client and user satisfaction. To achieve that level of quality, a group of non-functional testing methods was established to cover all areas of performance indicators, these methods are mainly designed in a way that makes it difficult for manual testing and instead mostly rely on automated testing tools.

Types of Non-functional Testing:

Load testing – It is the process of assessing the behavior of a system in a simulated environment under predicted conditions (various numbers of users).

Stress testing – A testing method that evaluates performance when resources are scarce, such as when a server is down or there is not enough capacity on a device’s hard drive.

Scalability testing – This testing method determines whether a system can scale with additional usage and, if so, how much the performance is impacted.

Security testing – A process of testing that determines how vulnerable a system is to attack and safeguard data.

Volume testing – it evaluates performance with a large amount of data, not necessarily involving many users, but rather a single person executing a high-volume job, such as multiple-file uploading.

 (Functional Testing VS Non-Functional Testing)

Functional TestingNon-Functional Testing


validating software actions.ensuring that the software performs as expected.
ExecutionIt is carried out before non-functional testing.This is done when the functional testing is completed.
UsageAssists in the validation of the application’s behavior.Assists in validating the application’s performance.
Testing toolsIt can simply rely on manual efforts.It is extremely difficult to execute manually. (Automated testing tools are used)
RequirementIt is done based on business requirements.It is done based on customer expectations and performance requirements as defined by IT.


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