Functional Testing Vs Non-Functional Testing

Know the Difference Between Functional Testing Vs Non-Functional Testing with Examples:

Software Testing is broadly categorized into Functional and Non- Functional Testing.

Let us discuss in detail about these testing types along with the exact differences between both functional and non-functional tests. 

Functional Testing Vs Non-Functional Testing

What is Functional Testing?

Functional testing is testing the ‘Functionality’ of a software or an application under test.

It tests the behavior of the software under test. Based on the requirement of the client, a document called a software specification or Requirement Specification is used as a guide to test the application.

A test data is sculpted based on it and a set of Test Cases are prepared. The software is then tested in a real environment to check whether the actual result is in sync with the expected result. This technique is called as Black Box Technique and is mostly carried out manually and is also very effective in finding bugs.

Further reading => What is Functional Testing – a Complete Guide

Let us explore the types of Functional Testing now!!

Types of Functional Testing

Enlisted below are the various types of Functional Testing.

Smoke Testing:

This type of testing is performed before the actual system testing to check if the critical functionalities are working fine in order to carry out further extensive testing.

This, in turn, saves the time of installing the new build again and avoids further testing if the critical functionalities fail to work. It is a generalized way of testing the application.

smoke and sanity testing

[image source]

Sanity Testing:

It is a type of testing where only a specific functionality or a bug which is fixed is tested to check whether the functionality is working fine and see if there are no other issues due to the changes in the related components. It is a specific way of testing the application.

Integration Testing:

Integration Testing is performed when two or more functions or components of the software are integrated to form a system. It basically checks the proper functioning of the software when the components are merged to work as a single unit.

Regression Testing:

Regression testing is carried out on receiving the build of the software after fixing the bugs that were found in the initial round of testing. It verifies whether the bugs are fixed and checks if the entire software is working fine with the changes.

Localization Testing:

It is a testing process to check the software’s functioning when it is transformed into an application using a different language as required by the client.

Example: Say a website is working fine in English language setup and now it is localized to Spanish language setup. The changes in the language may affect the overall user interface and functionality too. Testing done to check these changes is known as Localization testing.

Localization Testing

User Acceptance Testing

In User Acceptance testing the application is tested based on the user’s comfort and acceptance by considering their ease of use.

The actual end users or the clients are given a trial version to be used in their office setup to check if the software is working as per their requirements in a real environment. This testing is carried out before the final launch and is also termed as Beta Testing or end-user testing.

What is Non-Functional Testing?

There are some aspects which are complex such as Performance of an application etc and this testing checks the Quality of the software to be tested. Quality majorly depends on Time, Accuracy, Stability, correctness and durability of a product under various adverse circumstances.

In software terms, when an application works as per the user’s expectation, smoothly and efficiently under any condition, then it is stated as a reliable application. Based on these aspects of quality, it is very critical to test under these parameters. This type of testing is called Non- Functional Testing.

It is not feasible to test this type manually, hence some special automated tools are used to test it.

Example tools: LoadRunner, JMeter etc.

Further reading => What is Non-Functional Testing – a Complete Guide

Types of Non-Functional Testing

Given below are the various types of Non-Functional Testing.

Performance Testing:

performance tsting

#1) Load Testing: An application which is expected to handle a particular workload is tested for its response time in a real environment depicting a particular workload. It is tested for its ability to function correctly in a stipulated time and is able to handle the load.

#2) Stress Testing: In Stress testing, the application is stressed with an extra workload to check if it works efficiently and is able to handle the stress as per the requirement.

Example: Consider a website which is tested to check its behavior when the user accesses is at its peak. There could be a situation where the workload crosses beyond the specification. In this case, the website may fail, slow down or even crash.

Stress testing is to check these situations using automation tools to create a real-time situation of workload and find the defects.

#3) Volume Testing: Under Volume testing the application’s ability to handle data in the volume is tested by providing a real-time environment. The application is tested for its correctness and reliability under adverse conditions.

#4) Endurance Testing: In Endurance testing the durability of the software is tested with a repeated and consistent flow of load in a scalable pattern. It checks the endurance power of the software when loaded with a consistent workload.

Endurance Testing

All these testing types are used to make the software work bug-free and crash free under any real time situation by addressing the issues and finding solutions accordingly for a quality product.

Usability Testing:

In this type of testing the User Interface is tested for its ease of use and see how user-friendly it is.

Security Testing:

Security Testing is to check how secure the software is regarding the data over the network from malicious attack. The key areas to be tested in this testing include authorization, authentication of users and their access to the data based on the roles such as admin, moderator, composer, and user level.

Thus after knowing the definitions, one can get a clear idea of the difference between functional and non-functional testing.

Difference Between Functional and Non-Functional Testing

Functional TestingNon Functional Testing
It tests ‘What’ the product does. It checks the operations and actions of an Application.It checks the behaviour of an Application.
Functional testing is done based on the business requirement.Non- functional testing is done based on the customer expectation and Performance requirement.
It tests whether the actual result is working according to the expected result.It checks the response time, and speed of the software under specific conditions.
It is carried out manually.
Example: Black box testing method.
It is more feasible to test using automated tools.
Example: Loadrunner.
It tests as per the customer requirements.It tests as per customer expectations.
Customer feedback helps in reducing the risk factors of the product.Customer feedback is more valuable for non- functional testing as it helps to improve and lets the tester to know the expectation of the customer.
It is testing the functionality of the software.It is testing the performance of the functionality of the software.
Functional testing has the following types:
•Unit testing
•Integration testing
•System Testing
•Acceptance Testing
Non functional testing includes:
•Performance testing
•Load Testing
•Stress testing
•Volume testing
•Security testing
•Installation testing
•Recovery testing
Example: A Login page must show textboxes to Enter the username and password.Example: Test if a Login page is getting loaded in 5 seconds.


Hope you would have gained a basic understanding of both Functional and Non-Functional Testing.

We have also explored the types, and differences between functional and non-functional testing.

Happy Reading!!