What is Functional Testing and Types of Functional Testing?

Functional Testing is one of the testing techniques, which assists the team remarkably in verifying the quality as well as functionality of the software. Functional testing process enables the team to validate whether or not the software is fixed and ready for its release. Hence, to define the importance of functional testing, following is a detailed discussion on the same.

What is meant by Functional Testing??

Functional Testing
Functional testing, as the name suggests, means to check the functionality of the software based on SRS (Software Requirements Specification).The main objective of functional testing is to validate the functionality of the software and ensure that it is in compliance with the business requirements, stated by the client before the commencement of the project.

After the development stage of a software product is over, it requires to be tested on the basis of its chief specifications, such as user commands, search operations, and more. This is achieved with the assistance of functional testing, which subtly defines what a system does and validates its accuracy.

Features of Functional Testing:

From verifying the functionality of the software to ensuring its features and components, functional testing has a major role to play in software testing life cycle (STLC). Therefore, to help you better understand the significance of this testing technique, here are some of its features:

  • Functional testing is a process of quality assurance.
  • It validates the functionality of the web applications and ensures that they conform to their specific functional requirements.
  • It is a type of black box testing.
  • The functional test cases are based on the specifications of the component under test.
  • It tests the functionality and the features of the software.
  • Functional testing is not concerned with how the system processes.
  • This type of software testing does not require internal knowledge of the software structure.
  • It verifies the various aspects described in the requirement specification and function specification document.
  • Functional Testing is a specification based testing.

What are the different types of Functional Testing?

Since, functional testing tests various aspects of a software product, the types of testing that are performed under this methodology of software testing are numerous. Therefore, the different types of functional testing are:

  • Unit Tests: Unit testing tests the individual components of the software and validates their performance as per the specified requirements.
  • Integration Testing: Performed with the assistance of stubs and drivers, integration testing involves testing of individual units by combining and testing them in a group. Integration testing aims at exposing issues and defects in the interaction between various integrated units.
  • Sanity Testing: It tests the logical reasoning pertaining to the working of the program. For example, it can check if the result arising out of a calculation is true or incorrect.
  • Smoke Testing: One of the most preliminary of tests, smoke testing reveals the most elementary of errors. It addresses the most basic of functionalities crucial to the working of the product. It addresses questions like, "Can the program run?" "Is the window opening on pressing the click button?"
  • User Acceptance Testing: As the name suggests, user acceptance testing involves creation of a scenario where the targeted customers or the end users get a chance to review the functioning of a product. This can be something as basic as testing the attachment function in Gmail.
  • Regression Testing: Many a times, a bug is revealed in the functioning of an application, post minor variation in its configuration due to an upgrade. This is called a regression. The aim of regression testing is to eliminate any such eventuality and make the product resistant to glitches in the aftermath of a patch or upgrade.

Functional Testing Infographic

Functional Testing Infographics

Functional Testing Process

Contrary to popular belief, functional testing can be and should be performed in the beginning of the software development stage. Pretty much a black box testing technique, it involves initial feeding of input data to the system and a subsequent validation of the response, against the main specifications. In short, the functional testing process can be summarized into few important points, which are:

  • The expected functionality of the software product is identified.
  • Test data is utilized by the team to identify the inputs.
  • Once identified, the team creates input data on the basis of the functional specification.
  • Test cases are executed with proper inputs.
  • Finally, the results derived from the executed tests is compared with the expected output.
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Functional Testing Techniques:

During the process of functional testing, two major techniques are used by the team of testers. Each of these cater to different aspects of the software and work together to improve the quality as performance of the software. These techniques are:

  1. Requirement Based Testing: During this type of testing the requirements are prioritized by the team on the basis of the risk criteria, after which most critical and important features and functions of the software are evaluated and tested.
  2. Business Process Based Testing: This type of functional testing relies on the knowledge of business processes, based on which the scenarios for testing are described.

Apart from these two techniques, functional testing also uses the white box testing and black box testing techniques to run the tests and to ensure the quality as well as the functionality of the software product.

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Functional Testing Checklist:

The importance of creating a check-list before the beginning of any process is quite well known to us. Likewise, it is crucial for us to prepare a functional testing checklist, which can help us track the progress of functional testing.

Therefore, here is a check-list for functional testing.

  • Identify and define the objective of testing.
  • Understand the business requirements and specifications.
  • Bring together a team of dedicated individuals for the process of testing.
  • Create a plan or test strategy before the commencement of the process.
  • Test cases should be designed to stimulate the flow of activities.
  • Prioritize critical features and aspects of the product and test them first.
  • Find an appropriate tool for the process of testing.

Get a detailed overview of functional testing checklist here.

Functional Testing Tools List:

Apart from manual testing, the process of functional testing can also be executed with the assistance of various tools available in the market. These tools simplify the process of testing and help the team get accurate and effective results.

Hence, here is a list of important automation tools used for functional testing:

For a detailed list of functional testing tools, click here.

Difference Between Functional Testing & System Testing:

Functional Testing System Testing
1. Functional testing is a part of system testing. 1. Tests are executed to verify the compliance of the completed and integrated software with its specifications.
2. Verifies the functionality of the product and ensures it works as per its specifications. 2. Its purpose is to ensure that the completed product fulfills the stated requirements.
3. Tests the functionalities and features of the software, such as load, security, performance and more. 3. It is performed to the test the end product.
4. Manual testing and automation test tools can be used for functional testing. 4. It tests every single module, interface and internal and external aspects of the software.
5.It helps define what the product does. 5.It defines how good a software works.
6. Does not require internal knowledge of the structure. 6. System testing is performed after integration testing and before acceptance testing.

Functional Testing vs Non Functional Testing:

You can also read about the differences between functional and non-functional testing, here.

Advantages and Disadvantages of Functional Testing:


Lets highlight various advantages of Functional Testing.

  • Functional testing is essential for evaluating the performance and the functionality of a software application before it is delivered to the end user for its real use.
  • It is performed from the perspective of the users, which allows the development team to create test scenarios that represent the real world use scenarios.
  • Allows the team to meet the requirements of the user as well as the client.
  • It helps improve actual system usage.
  • Enhances the quality of the software product.


Listed below are the various disadvantages of Functional Testing:

  • Functional testing can miss critical as well as logical errors in the system.
  • The possibility of conducting redundant testing is high in functional testing.
  • This testing cannot guarantee the readiness of the software to go live.


From the above discussion, we can easily conclude that to build a strong foundation of a top class software product, functional testing is essential. It acts as a bedrock of the structure and is a crucial part of every test routine.

Read about non-functional testing and give a boost to your knowledge, immediately.


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