What is the Difference Between Functional and Nonfunctional Testing

The main difference between functional and nonfunctional testing is that the functional testing is the type of testing that ensures that the software product is working properly while the nonfunctional testing is the type of testing that checks the nonfunctional aspects such as performance, usability, reliability etc. of the software.

Software testing is an important task in software development. It is the process of verifying and validating that the software product is working to the expectation. There are various types of testing, and functional and nonfunctional testing are two of them. Functional testing verifies that the system is tested against the functional requirements or specifications. On the other hand, nonfunctional testing verifies the attributes of the system such as robustness, performance, etc. Both these testing types are important to produce a working and reliable software at the end.

Key Areas Covered

1. What is Functional Testing
     – Definition, Functionality
2. What is Nonfunctional Testing
     – Definition, Functionality
3. What is the Difference Between Functional and Nonfunctional Testing
    – Comparison of Key Differences

Key Terms

Functional Testing, Nonfunctional Testing, Software Testing

What is Functional Testing

Functional testing is the type of testing that ensures that the software product works according to the requirements. In this testing, we test all the functionalities of the product. The tester can provide appropriate inputs and check the outputs. Then he can compare the actual results with the expected results. This testing involves checking user interfaces, APIs, databases, etc.

Figure 1: Software Testing

For example, assume a software such as medical center management system. This system has a number of functionalities such as adding, updating, deleting patient details, adding, updating deleting doctor details, general reports, print bills, etc. Checking whether each of the functionality work as expected is functional testing.

What is Nonfunctional Testing

Nonfunctional testing is a type of testing that checks the nonfunctional aspects of the system. It focuses on different aspects such as performance, usability, reliability etc. In other words, it tests the parameters that are not tested in functional testing. However, nonfunctional testing is equally important as functional testing. It also helps to get client acceptance.

Checking how the system works for anticipated workload, checking the system for extreme workloads, checking how the software handles the expected workload for a period of them and checking how the system works to sudden loads are few examples for nonfunctional testing. 

Difference Between Functional and Nonfunctional Testing

Definition

Functional testing is a software testing process used within software development where software is tested to ensure that it conforms with all requirements. Conversely, nonfunctional testing is a type of testing that checks the way a system operates rather than specific behaviors of the system. Hence, this explains the main difference between functional and nonfunctional testing.

Order of Execution

Another difference between functional and nonfunctional testing is that we perform the functional testing before the nonfunctional testing.

Requirements

Furthermore, defining the requirement also contributes to the difference between functional and nonfunctional testing. That is; it is easier to define requirements for functional testing. However, it is difficult to define requirements for nonfunctional testing.

Functionality

Functional testing describes what the product does whereas nonfunctional testing describes how the product works. Hence, this describes the difference between functional and nonfunctional testing in brief.

Usage

Moreover, functional testing helps to validate the system behavior. In contrast, nonfunctional testing helps to validate the way the system operates.

Testing Types

Unit testing, integration testing, and user acceptance testing are some types of functional testing. Conversely, performance testing, load testing, and, stress testing are some types of nonfunctional testing.

Example

Checking the login functionality is an example for functional testing. Checking how many users can log in to the system simultaneously is an example for nonfunctional testing.

Conclusion

The difference between functional and nonfunctional testing is that the functional testing is the type of testing that ensures that the functionalities of the software are working properly while the nonfunctional testing is the type of testing that checks the nonfunctional aspects such as performance, usability, reliability etc. of the software.

 Reference:

1. “Functional Testing.” Wikipedia, Wikimedia Foundation, 1 June 2018, Available here.
2. “Non-Functional Testing.” Wikipedia, Wikimedia Foundation, 10 Aug. 2017, Available here.

Image Courtesy:

1. “762486” (CC0) via Pixabay