Difference Between Functional vs. Nonfunctional Testing

4 min readMar 9, 2023

When it comes to application testing, many developers often think of unit tests and integration tests. While these types of tests are important, they alone are not sufficient to ensure a high quality production codebase. To achieve this, a comprehensive testing process that includes both functional and nonfunctional tests is necessary.

What is Functional Testing?

Functional testing is a crucial aspect of this process. It involves evaluating an application’s functionality and comparing it to specified requirements or specifications. By testing portions of the code and evaluating actual outputs against expected results, functional testing can uncover potential errors that may not be revealed by testing individual modules in isolation.

There are several subtypes of functional testing, including unit testing (which can also be used for non­functional testing), integration testing, user acceptance testing, and closed box testing. Each of these types has its own unique purpose and can help ensure that the application is functioning as intended.

Elements of Functional Testing

To ensure a comprehensive functional testing process, it’s important to concentrate on several key areas. These include:

Major functionalities: This involves testing the application’s core features and ensuring that they meet customer requirements. By providing input data and analyzing the results, you can verify that the application is operating properly.

Basic usability: It’s important to ensure that the application is easy to use and navigate for users. Testing basic usability can help identify any areas of the application that may need improvement to provide a better user experience.

Error validation: When erroneous or inaccurate information is provided, error validation involves looking for the proper error messages. By testing error validation, you can ensure that the application responds appropriately to errors and that users are provided with helpful error messages.

What is Non­functional Testing ?

When it comes to mobile applications testing, it’s important to assess not just their functionality, but also their behavior and performance. This is where non­ their functionality, but also their behavior and performance. This is where nonfunctional testing comes into play. Non­functional testing is a category of testing that includes several subcategories, such as performance, load, stress, volume, security, update and installation, and recovery tests.

So, what sets non­functional testing apart from functional testing? While functional testing ensures that an application complies with requirements and specifications, non­functional testing focuses on assessing the application’s performance, dependability, and security.

Elements of non­functional testing?

The following are some essential elements of non­functional testing that you should consider:

Security: Non­functional testing should include an assessment of the application’s security to identify potential threats, dangers, or vulnerabilities. By doing so, you can help ensure that your application is secure and protects sensitive information.

Usability: During non­functional testing, you should evaluate the application’s ability to interact with users. This includes analyzing the system’s capacity for operation, input and output analysis, and user learning. By testing usability, you can identify areas of the application that may require improvement to provide a better user experience.

Scalability: Non­functional testing should evaluate the system’s ability to increase its processing power in response to rising demand. By testing scalability, you can identify any potential performance bottlenecks and ensure that the application can handle increased user demand.

Interoperability: Non­functional testing should also measure the application’s ability to interact with other systems, such as Bluetooth data transfer. By doing so, you can help ensure that your application is compatible with other systems and technologies.

Efficiency: In non­functional testing, an application system’s response time is assessed in terms of efficiency. By testing efficiency, you can identify areas of the application that may require optimization to improve overall performance.

Flexibility: During non­functional testing, you should evaluate the application’s ability to run in various hardware and app configurations, such as minimal RAM and CPU requirements. By doing so, you can help ensure that your application is compatible with a wide range of systems and devices.

What’s the difference between functional and nonfunctional testing types?

The difference between functional and non­functional testing types lies in what is tested. Functional testing checks that an application’s features and functions work as intended. Non­functional testing, on the other hand, assesses several performance characteristics of the application, such as its speed, scalability, security, and more.

Why You Can’t Afford to Skip Nonfunctional Testing

It is essential to conduct both types of testing because neglecting non­functional testing may lead to negative user experiences, brand harm, and security vulnerabilities. It is a mistake to underestimate non­functional testing, even though its benefits may be less visible than functional testing. Including nonfunctional testing as a crucial component of the application development process is critical to producing reliable and efficient products.

While functional testing is typically less costly and time-consuming than nonfunctional testing, it is equally important to the overall success of an application. Ignoring functionality errors can result in poor usability and reduced accessibility to crucial features, which may have a negative impact on user satisfaction.


In conclusion, understanding the distinctions between functional and nonfunctional testing is crucial in delivering a high ­quality software application. While both forms of testing are important, the appropriate strategy depends on the particular context and needs of the application. By prioritizing both functional and non­functional testing, you can ensure a reliable and efficient product that meets the needs of your users.




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