Difference between Functional and Non-Functional Testing

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The two terminologies a tester would hear all day long in his testing career are functional and non-functional testing.

There are more than 50 types of testing in the industry, but all of them can primarily be divided into these two. Functional testing is where the tester tests the product on the features listed by the client that needs to be added, like the login feature, comment section, and mailing functionality. Non-functional testing is primarily about the site's performance, speed, scalability, etc.

What is Functional Testing?

As the name suggests, functional testing tests the application against functional requirements and specifications. Functional requirements are the list of features specified by the client that needs to be added to the product.

The specifications include UI, API, and database. For example, the client asked for an authentication system that needs to have Gmail, Facebook, and Regular signup. Testing all that scenarios for user interaction, backend operations, and core functionality.

Types of Functional Testing

  1. Unit Testing
  2. Integration Testing
  3. System Testing
  4. Regression Testing
  5. Database Testing

What is non-functional testing?

Non-functional testing tests the application's behaviour, aspects like performance, stress, load, and volume of the server. These are all quantitative measures. These are not part of the features a user can see but more about the reliability factor of the application.

For example, a user might not be able to know that a given instance site is capable of handling 100K users. This is not a feature for a site user but an essential product aspect. Functional and non-functional testing hence are very different from each other.

Types of Non-Functional Testing

  1. Performance Testing
  2. Load Testing
  3. Stress Testing
  4. Volume Testing
  5. Scalability Testing

Functional Vs. Non-Functional Testing

CriteriaFunctional TestingNon-Functional Testing
DefinitionIt validates the features of the productIt validates the behavior aspect of the product
ObjectiveEnsure the listed functionality of the application is workingEnsure Speed, Performance, and Usability factors are working
Manual TestingExploratory and manual testing coverage is thereNon-functional testing cannot be done manually
Automation TestingRepetitive and Redundant test cases are automatedAll non-functional requirements are automated
Case studyTesting login functionality of application through manual and automated test casesTesting performance and load of the site using apache Jmeter tool
Types1.Unit Testing
2.Integration Testing
3.System Testing
4.Regression Testing
5.Database Testing
1. Performance Testing
2. Load Testing
3. Stress Testing
4. Volume Testing
5. Scalability Testing


  1. In this article, we discussed the difference between functional and non-functional testing. Functional testing comprises test cases that validate the application's core features.
  2. Smoke Testing, Unit Testing, and Database Testing are all types of functional testing.
  3. Non-functional testing comprises the behaviour aspect of the system, i.e., performance, stress, etc.
  4. Performance testing, usability testing, and volume testing are all types of non-functional testing.

See More

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