Differences between Functional and Non-functional Testing

Functional Testing:
Functional testing is a type of software testing in which the system is tested against the functional requirements and specifications. Functional testing ensures that the requirements or specifications are properly satisfied by the application. This type of testing is particularly concerned with the result of processing. It focuses on simulation of actual system usage but does not develop any system structure assumptions.

It is basically defined as a type of testing which verifies that each function of the software application works in conformance with the requirement and specification. This testing is not concerned about the source code of the application. Each functionality of the software application is tested by providing appropriate test input, expecting the output and comparing the actual output with the expected output.

Non-functional Testing:
Non-functional testing is a type of software testing that is performed to verify the non-functional requirements of the application. It verifies whether the behavior of the system is as per the requirement or not. It tests all the aspects which are not tested in functional testing.

Non-functional testing is defined as a type of software testing to check non-functional aspects of a software application. It is designed to test the readiness of a system as per nonfunctional parameters which are never addressed by functional testing. Non-functional testing is as important as functional testing.

Below is the difference between functional and non-functional testing:

Functional Testing Non-functional Testing
It verifies the operations and actions of an application. It verifies the behavior of an application.
It is based on requirements of customer. It is based on expectations of customer.
It helps to enhance the behavior of the application. It helps to improve the performance of the application.
Functional testing is easy to execute manually. It is hard to execute non-functional testing manually.
It tests what the product does. It describes how the product does.
Functional testing is based on the business requirement. Non-functional testing is based on the performance requirement.
Examples:

1. Unit Testing
2. Smoke Testing
3. Integration Testing
4. Regression Testing 
Examples:

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



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