Functional testing and its types

Functional testing and its types

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Updated on Nov 3, 2022 10:15 IST

Functional testing is used to verify the functionality of the software application, whether the function is working according to the requirement specification.In this article we will focus on Functional testing and its types.It also includes steps of doin functional testing.


Software testing is a method to detect errors and bugs in computer software before the end-users use it. Continuous software testing is a must to avoid software development issues, but it is costly and time-consuming. Therefore, it is necessary to do quality assurance (QA) activities at the development stages. Testing activities are performed at various stages of software development and can be manual or automated. Some testing techniques include unit testing, integration testing, stress testing, system testing, and acceptance testing. All these techniques have different advantages and disadvantages. Hence, it’s essential to know the concept of functional testing before writing a test plan.In this article we will focuss on Functional testing and its types.

Table of contents

What is functional testing?

Functional testing is an activity performed to check the functionality of a program before its release. It is also known as non-regression testing or bug checking. This process involves executing the complete program under controlled conditions to ensure that it performs as expected and no errors occur. A tester performs this activity manually or using an automated tool. These tests should be performed frequently during the development phase to find any new bugs in the code and update the code accordingly. During regression testing, the program is tested after any changes are made and should not encounter any errors.

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Procedure for functional testing

1. Identify test objectives 

The goal of functional testing is the functionality that the software should have based on the requirements of the project. The purpose of testing includes verifying that the application is working as intended and gracefully handling errors and unexpected scenarios.

2. Create a test scenario

Create a list of all possible (or at least the most important) test scenarios for a particular feature. The test scenarios demonstrate different ways of using the feature. For example, a payment module test scenario can include multiple currencies, handle invalid or expired card numbers, or generate notifications indicating successful transactions. 

3. Create test data 

 Create test data that simulate normal usage conditions based on the test scenario you identified. Test data can be entered manually (from MS Excel spreadsheets or formulas) or automatically via scripts or test tools that read and enter data from databases, flat files, XML, or spreadsheets. Each input data set also requires associated data that describes the expected result that the input data produces.

4. Run test cases

Run the test cases on your application and compare the actual and expected results. If the actual output differs from the expected output, the function fails the test, and a defect is logged.

5. Conscious Detection, Tracking, and Correction of Errors

Once a bug has been identified, it should be recorded in a formal tracking system accessible to the entire project team. You should make the necessary changes to your application, rerun the test case to see the solution, and then mark the bug as closed.

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Types of functional testing

1. Unit Testing

Unit testing is a crucial practice in software engineering. It’s used to verify the functionality of individual software components. This process is fundamental in the development of large-scale software projects. Not all developers focus on unit testing, even though it’s essential in software creation. This process is typically carried out by developers familiar with the source code being tested. 

2. Integration testing

Integration testing is testing in which software modules are logically integrated and tested as a whole group. A typical software project consists of multiple software modules coded by different programmers. This testing aims to find bugs in the software modules when they are integrated.

3. System testing 

System testing is a type of software development testing that is used to check the overall functionality of your project. It is performed before any other software development phases. It helps identify bugs and problems in your project’s software before you start developing it. It also helps you verify that your project meets your goals and specifications. 

4. Acceptance testing 

Acceptance testing is a method used to test software applications before releasing them to the public. It’s a form of software development testing and typically involves a team of stakeholders, developers, and subject matter experts. This process involves manually testing the application to ensure it functions as expected by the target audience. It’s an effective way to prevent bugs in new software and identify errors early on.

5. Smoke Testing

Smoke tests cover only the basic (functional) functionality of the system. Smoke tests are called “build verification tests.” Smoke tests are meant to make sure the most important features work.

For example, the smoke test verifies that the application launches successfully and verifies that the GUI is responsive.

6. Acceptance testing

Acceptance testing is a method used to test software applications before releasing them to the public. It’s a form of software development testing and typically involves a team of stakeholders, developers, and subject matter experts. This process involves manually testing the application to ensure it functions as expected by the target audience. It’s an effective way to prevent bugs in new software and identify errors early on. There are two types of acceptance testing: alpha and beta testing.

7. Regression testing

This type of testing focuses on ensuring that code changes do not break the system’s existing functionality. Regression testing shows when an error occurs in the system after the error has been fixed. Regression testing focuses on whether all parts work. Regression testing focuses on whether the system is impacted.

8. White box testing

White-box testing (also known as clear-box testing, glass-box testing, transparent-box testing, and structural testing) tests an application’s internal structure or behavior instead of its functionality (that is, black-box testing). Software testing methodology). White-box testing uses an internal view of the system to design test cases. Testers choose inputs to practice code paths and determine expected outputs. White-box testing can be applied at the software testing process’s unit, integration, and system levels.

9. Black box testing

Black Box Testing, also known as Function Testing, is a powerful technique to test the functionalities of software applications without an in-depth understanding of the software’s internal logic or source code. In a nutshell, “black box testing is a technique that examines software’s functionality without examining its internal structure or coding.”

10. Greybox testing 

Greybox testing is a software testing technique for testing a software product or application using partial knowledge of the application’s internals. The purpose of gray box testing is to find and isolate bugs that result from improper code structure or improper application usage.

This process often identifies context-specific errors related to web systems. Expand your testing by focusing on all layers of a complex system.

11. Retesting

Retesting is a type of testing that is performed after a bug has been fixed to ensure that test cases that failed on the last run pass successfully. Testers usually assign bugs when they find them while testing a product or its components. Bugs are assigned to developers, who fix them. Once bugs are fixed, they are assigned to testers for review. This test is called a repeat test.

12. Recovery Tests

Recovery tests are used to define how well an application can recover from crashes, hardware failures, and other problems. Recovery testing aims to ensure that the system can recover from a failed test point.

 13. Static Testing

Static testing is a software testing technique that allows the software to be checked for bugs without actually running the software. Static testing is done to avoid bugs in the early stages of development, as bugs are easier to find in the early stages of development. Static testing is used to detect bugs that cannot be detected by dynamic testing.


In software testing, functional testing is the process of testing the functionality of a system, ensuring that the system behaves according to the functionality specified in the business document. The purpose of this test is to check if the system is working!!!

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