Functional Vs Non-Functional Testing – Difference Between Them

Key Difference Between Functional Testing and Non Functional Testing

Functional testing verifies each function/feature of the software whereas Non Functional testing verifies non-functional aspects like performance, usability, reliability, etc.
Functional testing can be done manually whereas Non Functional testing is hard to perform manually.
Functional testing is based on customer’s requirements whereas Non Functional testing is based on customer’s expectations.
Functional testing has a goal to validate software actions whereas Non Functional testing has a goal to validate the performance of the software.
A Functional Testing example is to check the login functionality whereas a Non Functional testing example is to check the dashboard should load in 2 seconds.
Functional describes what the product does whereas Non Functional describes how the product works.
Functional testing is performed before the non-functional testing.

What is Functional Testing?

Functional testing is a type of testing which verifies that each function of the software application operates in conformance with the requirement specification. This testing mainly involves black box testing, and it is not concerned about the source code of the application.

Every functionality of the system is tested by providing appropriate input, verifying the output and comparing the actual results with the expected results. This testing involves checking of User Interface, APIs, Database, security, client/ server applications and functionality of the Application Under Test. The testing can be done either manually or using automation

What is Non-Functional Testing?

Non-functional testing is a type of testing to check non-functional aspects (performance, usability, reliability, etc.) of a software application. It is explicitly designed to test the readiness of a system as per nonfunctional parameters which are never addressed by functional testing.

A good example of non-functional test would be to check how many people can simultaneously login into a software.

Non-functional testing is equally important as functional testing and affects client satisfaction.

Difference between Functional Testing and Non Functional Testing

Parameters	Functional	Non-functional testing
Execution	It is performed before non-functional testing.	It is performed after the functional testing.
Focus area	It is based on customer’s requirements.	It focusses on customer’s expectation.
Requirement	It is easy to define functional requirements.	It is difficult to define the requirements for non-functional testing.
Usage	Helps to validate the behavior of the application.	Helps to validate the performance of the application.
Objective	Carried out to validate software actions.	It is done to validate the performance of the software.
Requirements	Functional testing is carried out using the functional specification.	This kind of testing is carried out by performance specifications
Manual testing	Functional testing is easy to execute by manual testing.	It’s very hard to perform non-functional testing manually.
Functionality	It describes what the product does.	It describes how the product works.
Example Test Case	Check login functionality.	The dashboard should load in 2 seconds.
Testing Types	Examples of Functional Testing Types Unit testing Smoke testing User Acceptance Integration Testing Regression testing Localization Globalization Interoperability	Examples of Non-functional Testing Types Performance Testing Volume Testing Scalability Usability Testing Load Testing Stress Testing Compliance Testing Portability Testing Disaster Recover Testing