This article will provide you with a comprehensive list of types of functional testing in software engineering you may need to conduct during testing the software.

There are multiple types of software testing that you should need to understand before going to test any application. Functional testing and non-functional testing are two main types of software testing that can be further divided into different types of testing.

What is Functional Testing

Functional testing is a type of software testing that checks the functionality of a software system and whether or not they work as expected. It involves performing tests that assess how well the system performs its every function by providing input and observing its output. If the output is matched with the expected result test pass, otherwise the test fails.

Functional testing comes under black-box testing that may not need to have an understanding of internal logic. It can be performed by the manual testers or by the automation testers. Functional testing is further divided into multiple types of testing.


Types of Functional Testing

There are different types of functional testing that software testers can do in order to ensure the quality and functionality of a software product. These tests include:


Unit Testing

Unit testing is a type of functional testing that checks the functionality of a unit. A unit is nothing but a module, component, or a single program of the application, which is a self-contained part of the application. Unit testing is white-box testing. It is mostly done by the developers as it requires logical or programming skills.

Normally software testing is done by the testing engineers; however, developers also used to do some type of testing at the time of development like unit testing.

They check the internal logic of the program like how programming statements work and make sure all the lines of the programs are executing correctly, whether they are getting their expected output or not with different types of inputs.

Integration Testing

Integration testing is a type of functional testing in which a developer or a tester checks the functionality of different parts of a software application as they are integrated together. They check the interactions between different parts of a system. This type of testing is often used to ensure that the various parts of the application work together as expected. It checks for compatibility between different parts of the system.

A complete software or application would have multiple sets of programs, modules, components, or units. These units would be communicating with each other like the output of one unit can be the input for the second unit of the application.

These components or units are integrated with each other and developers need to test the communication between each component of the software after integrating them.  This type of testing is called integration testing, which is also done by the developers at the level of integration.

However, integration testing can also be done by the tester on UI. Integration testing also comes under white-box testing that requires logical or programming skills.

Component Testing

Component testing is a type of software testing that focuses on individual components of a program. This type of testing is often used when the program is too large or complex to test as a whole. By testing the individual components, the tester can determine if each one works correctly and interacts correctly with the other components. Component testing can also help to identify problems with individual components and make corrections before the entire program is tested.

System Testing

System testing is a type of software testing that checks the functionalities and flows of a whole integrated system. This type of functional testing is done after integration testing when all the components are integrated to make a complete system but before the user acceptance testing. System testing is a type of black-box testing performed by the testers because it does not require any internal logic of the application.

In system testing, testers also check the non-functional behaviors of the application as a whole system.  So system testing relates to both functional and non-functional testing.


Regression Testing

Regression testing is a type of functional testing that is used to determine whether a change or update in software has caused any unintended effects. It is often used when bugs are fixed, new features are added, or when changes are made to an existing product in order to make sure that all the components of the system remain stable and do not break down even after new changes happen.  Regression testing can be done manually or with automated tools.

Regression testing is an exhaustive type of testing because it is performed by the testers again and again, so best practices are to perform regression testing by some automation tools like Selenium and Katalon Studio, etc.  Regression testing can also be used to identify and fix problems that have already been discovered in the software.

Smoke Testing

Smoke testing is a type of functional testing that is performed at the software build level where the tester checks the basic and most important functionalities of the application once a new build is given by the development team.

This type of testing is used to ensure that the software or application under test is ready for further testing. If the build is stable, testers will accept it and continue with the next phase of testing.  If any issue is found while checking the critical functionalities of the application, the testing team will return the build back to the development team to fix the issues.

Sanity Testing

Sanity testing is a type of functional testing that is used to ensure that the bugs are fixed properly and these modifications in the product do not have any further issues introduced in the system.

This type of testing is typically done after the new features have been added to the software or bugs are fixed, but before further regression testing is executed.  Sanity testing is performed to determine whether or not the tester should proceed with regression testing.  Sanity testing is done at the maintenance level when new changes are added to the software.

The main difference between smoke testing and sanity testing is that smoke testing is done at the initial level or build level of software development after two or three builds before doing any further testing, whereas sanity testing is performed before regression testing when new features are being added into the fully functional application or bugs are fixed.

Ad-hoc Testing

Ad-hoc testing is a type of software testing in which software is tested without the use of a pre-planned or formal test plan. Ad-hoc testing is typically used when it is not possible or practical to use a pre-planned test plan because the nature of the work requires that tests be conducted quickly and without prior planning.

While performing this testing, testers’ main intentions are to just break the system by randomly testing the functionalities of the application.

Interface Testing

Interface testing is a type of functional testing used to verify the proper functionality of an interface between two components, whether data is being passed successfully and correctly and whether or not communication between two or more systems or interfaces is being done accurately and securely.

Communication between different external and internal interfaces like APIs, databases, and application itself is tested in this type of testing.  Interface testing is also done to verify whether or not data is properly synced in all integrated interfaces.

It is used to identify and correct errors in the design and implementation of an interface. Interface testing is also used to test how users will interact with the interface that all communications and interactions are correct.

GUI Testing

GUI software testing is the process of verifying the functionality of a graphical user interface (GUI). GUI testing can be divided into three categories: functional, manual, and cognitive. Functional GUI testing verifies that all the functions of the GUI are working as expected. Manual GUI testing involves using a human tester to interact with the application and verify that all the buttons and elements work as they should, while cognitive GUI testing evaluates how users perceive and use the interface design by measuring their reaction time, error rates, and satisfaction levels.

API Testing

API testing is the process of testing the functionality of an application’s APIs. This includes verifying that calls made to an API conform to the expected behavior and checking for any potential issues with the implementation.

API testing is used to verify the correctness of data exchanged between systems, as well as the proper functioning of the API. This can be done manually or through automation tools like Postman, Katalon Studio, etc.

User Acceptance Testing

User acceptance testing, also known as UAT is a type of functional testing that is the final stage of the software development and testing process.

It is a type of black-box testing that is conducted to ensure that the system meets the requirements specified by the end users and that they are happy with the system’s performance. In UAT, end users test the system under realistic conditions to identify any issues or problems that may occur while using the system in the production environment.

User acceptance testing is also known as end-user testing because this type of testing is performed by the end-user or clients.  The goal of acceptance testing is not to find bugs, but to ensure that the software meets the real customer’s needs.

Alpha Testing

Alpha testing is the process of using a limited number of people to test the software in order to find and fix bugs before it is released to the general public.  Alpha testing is a subset of acceptance testing which is performed by the software testers to make sure the product is ready to release. It is also known as pre-release testing or early release testing.

Beta Testing

Beta testing is a process of testing a product or service with the intention of finding and resolving any issues before it is released to the targetted audience.  During beta testing, a limited number of selected end-users who are not part of the original target audience are recruited to help test the product. This allows for early identification and resolution of potential problems before they become widespread.

Black Box Testing

Black box testing is a type of software testing that involves testing the software without knowing the source code or how it works.  A tester creates test cases, executes them by putting the input, and then verifying that the software is producing the expected output.

White Box Testing

White Box Testing is a type of testing that focuses on the internal workings of a system or software application. This type of testing is typically performed by software developers or testers who have programming skills. Unit testing and integration testing comes under white box testing. White box testing is used to assert that the code segments are producing expected outcomes.

Production Testing

Production testing is a type of functional testing aimed at verifying the correctness of the software in its intended production environment. In the production environment, each user can interact with it in any way, so testers test the functionality and stability of the software in this environment by using a maximum number of real-world usage scenarios.

The goal of the production testing is to provide assurance that the software will meet the needs of end-users in a real-world setting. Production testing typically involves using actual user data, rather than simulated or test data, to identify and fix problems.

Installation Testing

Installation testing is the process of verifying that a software application or system can be installed, configured, and operated properly. The goal of installation testing is to ensure that the software meets the customer’s expectations when it is actually installed on their computer.

Installation testing may involve performing a variety of tasks, such as: verifying that all required files are present on the target system; checking for proper installation and configuration of components; verifying that all required dependencies are installed; determining whether any potential conflicts exist between installed applications; and ensuring that user rights settings are correct.


In conclusion, functional testing can be done in several different ways, depending on the specific needs of the software and types of functional testing as explained above.

The most important thing is to make sure that all the necessary functions are comprehensively tested and that the test cases cover all possible scenarios. By doing this, you can be sure that your software is ready for release and that any potential problems will be caught before they cause damage.

Completion of all types of functional testing will provide assurance that the software meets the customer’s expectations.