Functional Testing and Types of Them

Functional Testing and Types of Them

Functional testing is one of the 4 main types of Integration Test in software testing. So what is functional testing and what types are functional testing? Let’s find out together!

1. What is functional testing?

Functional testing is testing for the functionality of a software or an application. It checks the behavior of the software under test based on customer requirements called Software Requirements Specifications (SRS).

Functional testing is a type of black box testing and its test cases are based on the specification of the software application/component under test. Functions are tested by entering inputs and checking the output, with little related to the internal structure of the application.

Functional testing is a process that tries to find the differences between the external specification of the software and the reality that the software provides. With the external specification of the software is the exact specification of the software's behavior from the user's point of view

2. Purpose of functional testing

With functional testing, we verify that the software is not compatible with its external specifications.


-  Avoids redundancy testing

-  Prevent too much attention on too many types of errors at a time

3. Types of functional testing

1)  Smoke testing:

Smoke Testing is a process to check if the deployed build version is stable or not. Smoke Tests are a set of minimal tests that run on each build to confirm whether the QA team can continue with further testing,

In other words, we are verifying whether important features are working and there are no categories in the build that are being tested.

This will save time re-installing a new build and avoid further testing if important functions are not working.

2) Sanity Testing:

Sanity testing is executed after receiving the build of the software, with minor changes in the code or functionality. This is a type of testing in which only a specific function or a bug is fixed to check if the function is working properly or not.

In addition, sanity testing also checks if there are other problems due to the changes in the relevant components.

3) Integration Testing:

Integration testing is performed when two or more functions or software components are integrated to form a system. Integration testing takes unit-tested input modules, groups them into larger sets, applies the test cases defined in the integration test plan to that set, and provides output for the integrated system.

4) Regression Testing:

Regression testing is performed when receiving a software build after fixing the bugs found in the initial test (test round 1). Regression testing verifies if the bugs have been actually fixed and checks if the entire test is complete, whether the software suite works well with the changes.

5) Localization Testing:

Localization testing is a testing process to check the functionality of the software, when it is converted into an application using another language as required by the customer.

6) User Acceptance Testing:

In Acceptance Testing, the application is tested against the user's comfort and acceptance by considering their ease of use. Actual end users or customers are provided a trial version in their office setup to check if the software works according to their requirements in a real environment. This testing is done before the final launch and is also known as Beta Testing or end-user testing.


Functional Testing has a very important role in confirming whether the quality and functionality of the software is satisfactory or not. Each type of functional testing I introduced in this blog has different advantages and purposes, Depending on testing requirement, you should choose what type of functional testing when you plan testing software.