Functional Testing - Stuff You Must Know!


Functional testing 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.

Each and 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 do you test in Functional Testing?

The prime objective of Functional testing is   checking the functionalities of the software system. It mainly concentrates on -

  • Mainline functions:  Testing the main functions of an application
  • Basic Usability: It involves basic usability testing of the system. It checks whether an user can freely navigate through the screens without any difficulties.
  • Accessibility:  Checks the accessibility of the system for the user
  • Error Conditions: Usage of testing techniques to check for error conditions.  It checks whether suitable error messages are displayed.

Functional Testing Process:

In order to functionally test an application, following steps must be observed.

Functional Testing - Stuff You Must Know! Understand the Requirements
Functional Testing - Stuff You Must Know! Identify test input (test data)
Functional Testing - Stuff You Must Know! Compute the expected outcomes with the selected test input values
Functional Testing - Stuff You Must Know! Execute test cases 
Functional Testing - Stuff You Must Know! Comparison of actual and computed expected result

Functional Vs Non-Functional Testing:

Functional Testing

Non-Functional Testing

Functional testing is performed using the functional specification provided by the client and verifies the system against the functional requirements. Non-Functional testing  checks the  Performance, reliability, scalability and other non-functional aspects of the software system.
Functional testing is executed first Non functional testing should be performed after functional testing
Manual testing or automation tools can be used for functional testing Using tools will be effective for this testing
Business requirements are the inputs to functional testing Performance parameters like speed , scalability are inputs to non-functional testing.
Functional testing describes what the product does Nonfunctional testing describes how good the product works
Easy to do manual testing Tough to do manual testing
Types of Functional testing are
  • Unit Testing
  • Smoke Testing
  • Sanity Testing
  • Integration Testing
  • White box testing
  • Black Box testing
  • User Acceptance testing
  • Regression Testing
Types of Non functional testing are
  • Performance Testing
  • Load Testing
  • Volume Testing
  • Stress Testing
  • Security Testing
  • Installation Testing
  • Penetration Testing
  • Compatibility Testing
  • Migration Testing

Functional testing tools:

Functional Testing - Stuff You Must Know!There are several tools available in the marker to perform functional testing. They are explained as follows: 

  • JUnit - Used mainly for Java applications and this can be used in Unit and system testing
  • soapUI - This is an open source functional testing tool, mainly used for Web service testing. It supports multiple protocols such HTTP, SOAP and JDBC.
  • Watir - This is functional testing tool for web applications. It supports tests executed at the web browser and uses ruby scripting language


Functional testing is process of testing functionalities of the system and ensures that the system is working as per the functionalities specified in the business document. The goal of this testing is to check whether the system is functionally perfect!!!

Tutorial Index