The term “Functional Testing” refers to a type of black box testing. Assesses a system’s or component’s compliance with stated functional requirements. What the system does is specified by functional testing.

As the name implies, the test verifies that all of the application’s functionalities are working as expected and are ready for release. Because it is black box testing, the tester will not be aware of the app’s internal structure or source code.

The development team will create functional unit test cases based on user/business requirements, and testers will specify the functionality requirements from the user’s point of view. Functional testing can be performed manually or automatically by test teams.

Types of Test in Functional Testing?

Functional testing’s primary goal is to validate the component’s functionality.

Functional testing is divided into several sections. The following are the various types of functional testing.

Unit testing

It is a type of software testing in which a single unit or component of the software is tested. Unit testing examines various parts of the application; functional testing is also performed as a result of unit testing because unit testing ensures that each module is functioning properly.

The developer performs unit testing and it is carried out during the application’s development phase.

Smoke Testing

To evaluate critical system functionalities, smoke testing is performed once after developers publish the ‘new build,’ which is usually unstable. The goal of the testing is to validate the most important system functionalities rather than to run an tiring testing process. Critical functionality test cases are chosen, run, and validated. Smoke testing is performed by both testers and developers, and the testing is ‘build’ focused.

Sanity Testing

In testing, the terms “sanity testing” and “smoke testing” are used interchangeably. This is because both tests are run after the build is received. Sanity testing, a subset of regression testing, on the other hand, focuses on executing test cases related to build changes. In layman’s terms, a sanity test is run when a build, usually stable, is received with minor changes. It is carried out by testers and release focused.’

Regression Testing

This type of testing is concerned with ensuring that code changes do not interfere with the system’s existing functionality. Regression testing specifies when a bug recurs in the system after it has been fixed. Regression testing focuses on whether or not all parts are operational. This testing method focuses on whether or not there is any impact on the system.

Integration Testing

Individual units were combined and tested as a group during integration testing. The goal of this testing is to expose flaws in the interaction of the integrated units.

Integration testing is carried out by developers and testers.

White box testing

White box testing is also known as clear box testing, code-based testing, structural testing, extensive testing, glass box testing, and transparent box testing. It is a method of software testing in which the tester is aware of the internal structure/design/implementation under test.

White box testing necessitates an examination of the component’s or system’s internal structure.

Black box testing

It is also called as behavioural testing. The internal structure/design/implementation is unknown to the tester during this testing. This is referred to as functional testing. This type of testing is known as black box testing because the tester cannot see the internal code.

For example, a tester who is unfamiliar with the internal structures of a website may test the web pages through the use of a web browser to provide input and then comparing the output to the expected outcome.

User acceptance testing

It is a type of testing done by the client to certify the system in accordance with the requirements. Prior to releasing software to the market or production environment, the final phase of testing is user acceptance testing. UAT is a type of black-box testing that involves two or more end users.

How Functional Testing Works?

The following steps are involved in functional testing:

  • Determine the function to be performed.
  • Create input data based on function specifications.
  • Based on the function specifications, determine the output.
  • Carry out the test case.
  • Contrast the actual and expected results.

Example Of Functional Testing


A user logs in to an online HRMS portal using their user account and password. The login page includes two text fields for the username and password. There are also two buttons: Log in and Cancel.

When the login is successful, the user is directed to the HRMS home page. The cancel button terminates the login.


  • The user id field requires a minimum of 6 characters and a maximum of 10 characters, including numbers (0-9) and letters (a-z, A-z) (only underscore, period, hyphen allowed). It cannot be left empty. The user id must start with a number or character. It cannot contain any special characters.
  • The password field requires a minimum of 6 and a maximum of 8 characters, including numbers (0-9), letters (a-z, A-Z), and all special characters. It cannot be empty.

The above-mentioned use-case scenario can be tested using a variety of functional testing techniques.

End-user/System Testing

Check the system to see if all of the components are working properly together.

In this case, testing the customer journey would entail loading the HRMS application, entering accurate credentials, redirecting to the home page, performing tasks, and logging out of the system. This test ensures that the workflow continues and is completed without errors.

Boundary Values Test

These tests are used to see how the system behaves when data limits are set.

Because the user id requires a minimum of 6 characters in the example, this test will be used to see how the system responds when less than 6 characters are entered.

Ad-hoc Tests

These tests reveal discrepancies that may not have been detected by the other tests. Ad hoc tests are designed to break the system and test its response.

In this case, an ad hoc test could be performed to verify the following:

The administrator deletes a user’s account while the user is still logged in – and this while the user is performing tasks. The test would determine whether or not the application responded gracefully in such a scenario.

What are the Benefits of Functional Testing?

Some benefits of functional testing are listed below.

  • Functional testing creates a product that is free of flaws.
  • It ensures the customer’s satisfaction.
  • This type of testing ensures that all requirements have been met.
  • It ensures that all of an application’s/software’s/functionality products work properly.
  • Functional testing ensures that the software/product functions properly.
  • It guarantees security and safety.
  • This testing raises the product’s quality.

Related:- Unit testing vs functional testing

Wrap Up

We can easily conclude from this that functional testing is essential for laying the groundwork for a high-quality software product. It serves as the structure’s foundation and is an essential component of every test routine.

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