What is Functional Testing?

Functional testing means testing the application against business requirements. Functional testing is executed using the functional specifications given by the client or by the design specifications according to use cases given by the design team. Role of functional testing is to Validation the behavior of an application.

Functional testing is more important because it always verifies that your system is fixed for release. The functional tests define your working system in a useful manner. In functional testing tester has to validate the application to see that all specified requirements of the client whatever we have said in SRS or BRS have been incorporated or not.
Functional testing is always concentrating on customer requirements and whereas the Non-Functional testing is always concentrating on customer expectations.

Functional and Non Functional Test Cases

Functional test cases target business goals and non functional test cases target performance, resource utilization, usability, compatibility etc. Functional testing is a part of system testing.

Example of functional testing is explained below

Considering example if you are functionally testing a word processing application, a partial list of checks you would perform minimally includes creating, saving, editing, spell checking and printing documents.

Types of Functional Testing

Functional testing falls in to two categories:

1. Positive functional testing: - This testing carry exercising the application’s functions with valid input and also verifying that the outputs are correct.

Example:-

Again continuing with the word processing example, a positive test for the printing function might be to print a document containing both text as well as graphics to a printer that is online, filled with paper and for which the correct drivers are installed.

2. Negative functional testing: - This testing involves exercising application functionality using a combination of invalid inputs, some unexpected operating conditions and by some other “out-of-bounds” scenarios.

Example:-

Again continuing with the word processing example, a negative test for the printing function might be to disconnect the printer from the computers while a document is printing.

What probably should happen in these scenarios are a plain-English error message displayed, informing the user what happened and instructing him/her on how to fix the problem.

Conclusion:

At last we conclude that in functional testing functionality of the module is tested and structure is not considered. It is performed, based on user's perspective. These tests ensure that the system does what users are expecting it to do.

This type of testing means testing the functionality example include input the proper data and checking the output as per the requirement documents.