Functional Testing : Definition, Types & Examples

Functional testing is a type of software testing that validates the functionality of an application by means of automated tests. Functional testing does not ensure all data input, output, and internal structures work correctly. It only checks if the end product meets its required requirements.

A functional test is a test that checks whether a piece of software meets its intended functionality. Functional tests include unit testing, system testing, integration testing, and acceptance testing. A basic example of a functional test is to see if an application works properly when you click your smartphone’s home button.

Functional Testing Definition

In general, the definition of functional testing is a test that identifies defects before they cause an error or result in failure. However, this definition is just one way to look at it. In reality, functional testing includes more than finding bugs and inconsistencies in software functionality.

As per Wikipedia, the definition of functional testing is as follows:

Functional testing is a quality assurance (QA) process and a type of black-box testing that bases its test cases on the specifications of the software component under test. Functions are tested by feeding them input and examining the output, and internal program structure is rarely considered (unlike white-box testing). Functional testing is conducted to evaluate the compliance of a system or component with specified functional requirements. Functional testing usually describes what the system does.

What Is Functional Testing In QA?

Functional testing in QA (Quality Assurance) is a software testing technique used to evaluate the functionality of an application or system based on its specifications or requirements.

Functional testing involves checking the application or system against the functional requirements specified in the design or user documentation. It aims to ensure that the software application or system works as expected and meets the business requirements and user needs.

Functional testing, also called black-box testing, is software testing where the tester knows little about the internal structure or workings of the item being tested and mainly focuses on whether or not end users have access to what they need.

Why do we do Functional Testing?

Every application being developed has some functionality. That’s why it is the responsibility of testers to ensure that the application’s functionality meets business requirements and we are achieving whatever we intended through the design of this software.

Functional testing ensures that users can access all of the expected features in an application. Functional tests are written from a user perspective (not a programmer’s perspective) and include functionality such as login, search, shopping carts, etc.

During functional testing, QA or software testers are not concerned with finding defects; it is only focused on whether or not an application’s functions work or how users can do something in the system. It does not test for corner cases or error-handling routines.

Example :

An older system may not appear to work at all when you enter an incorrect delivery date on a new order. A tester would be looking for this behavior in functional testing and would fail the test if the application returned an error message or did not process the order. In other words, functional testing is focused on specific results and behaviors of the system under test as defined in a requirements specification or user story.

Functional testing is conducted by business analysts, users who use applications regularly, testers, and others with specific knowledge of the application’s business requirements.

Functional Testing Types

Functional testing includes various types of tests, such as:

Unit Testing – This type of functional testing is performed by the programmer who creates unit test cases to ensure that each function does what it is supposed to do given a specific input. Automated unit tests (unit tests written automatically by an IDE or other tool) are used here for this purpose when possible.

Test Scenario Testing- If you are using Agile methodologies to develop your application, then this type of functional testing is important because it ensures that the development team has included all the necessary business requirements. Test scenario testing is often a collaborative effort between programmers and testers.

Test Case Design- This type of functional testing involves designing tests that will validate each requirement in an application’s user story or task description. Test cases are then written for each requirement in a test plan.

Component Testing – This type of functional testing ensures that the major components of an application (such as a website’s login capability) work correctly. Component tests are usually based on programming code but do not require knowledge of the programmer’s coding language.

Smoke Testing– Smoke tests are quick, informal tests performed at the end of each iteration (a development period). Based on previous test results, smoke testing verifies that the latest code build works as expected.

Integration Testing– This type of functional testing is often used when several components or systems are being integrated together to form a larger application. Integration tests ensure that the different parts of the application work together according to specifications, and they can determine whether or not errors occur during integration between the various parts and modules.

Regression Testing– Regression testing is also called “retesting.” It determines if an application that previously passed functional tests still works correctly after a change.

Sanity Testing– Sanity testing is a quick test done during the early stages of development to ensure no show-stopper defects.

System Testing– System testing is the most formal type of functional testing. In this process, the system under test is put through its paces to determine if it works as expected based on the requirements specifications.

User Acceptance Testing– UAT stands for “user acceptance testing.” This type of testing is conducted as a final check of an application before it goes into production (the phase when the software is actually given to users). A representative of the application users conducts user acceptance testing. In some organizations, this may be a business representative or a customer.

White box testing- White box testing focuses on the internal structure of an application.

Black box testing- Black box testing attempts to test application functionality without knowing how it was programmed or designed.

Ad-hoc testing- Ad hoc testing is done without formal test plans or test cases.

Alpha testing: Alpha testing is done before beta testing to determine if a product has all the necessary features and works correctly. Alpha tests are typically conducted by employees of the organization developing the software or by third-party testers.

Beta Testing: Beta testing is often used when an application is about to be released to customers for evaluation purposes. Real users test the application, and results are analyzed to determine if any necessary changes need to be made before the application is released.

API testing- API testing is used to validate that an application programming interface (API) works as expected.

UI testing- UI testing is used to validate that a user interface works as expected.

Production testing: Production testing is used to validate that an application works as expected in a production environment.

What are the advantages of Functional Testing?

Testing is always necessary to see if the thing being tested will work as desired. We can test functionalities, applications, and even websites with these tests, which we have discussed above. Functional testing is always good because many benefits could be obtained from it.

The first advantage of conducting this type of testing is that it can find bugs, if there are any, in the program or website, we are going to use. Even though many developers will say there is no such thing as bug-free software, this testing can help us minimize the effect and ensure that the program won’t have too many issues.

Another advantage of functional testing is that it can be changed. If our website or application needs a different function, it will still be possible since we are only testing its functionalities.

It also helps us validate user requirements on what they need the program/website to do. This satisfies them once they see how exactly the software does and will work for them.

Finally, functional testing can be done automatically with the use of automation tools that are available in the market today. This is useful for us, especially if we have a lot of programs and websites to test since this could save time and money because it doesn’t need a human being to do its job. Automation also helps lessen our chances of making mistakes, especially regarding repetition.

What are the challenges of Functional Testing?

No matter how great functional testing is, some disadvantages could be gained from this type of test. One of which is the things that could make it fail and incorrectly perform its work. Even though we may not eliminate these factors, we can lessen them and know how to deal with them.

One of the biggest challenges that functional testing could have is its speed. Since it needs to test each function individually, much time will be consumed. If we always need to use it, this will delay creating or updating our program/application.

Another challenge is the skill of its tester or team developing it. There are different levels to test a software/website, which could be difficult for many, especially if they cannot handle them.

It also depends on what type of testing we need to use. We may only have one functional test, but to make it work, we must use the right ones according to our situation.

What are the best practices of Functional Testing?

A lot of best practices can be done while conducting this type of testing, and they could really help us out, especially if we know and understand them. It’s always good to remember these practices so we know what to do whenever a problem arises.

One of the most important is that we should always have great communication skills. Since this type of testing will involve many people, everyone needs to be able to talk and share their thoughts to enhance the process.

We should always follow a plan and know what needs to be done for the software/website to work perfectly. This will help us avoid any rushing issues, and if they already did, we can fix them immediately.

Another useful practice here is to have reported everything tested during each run so technicians or managers can check it. This will help them to have an overview of what was going on and how they could lower the risks of bugs occurring.

It’s also important for us to ensure that we are aware of all changes and updates that might affect the program/website. Making sure about this could save up time for us since we won’t be doing a lot of tests that are not needed.

We must also ensure that our program/website is stable and will not crash when launched. This could lower the reputation of potential users if this ever happens, which means that sales would decrease or even stop completely.

What is the future of Functional Testing?

Since many people are using functional testing, some new additions have been added. This would help us make it more efficient and better than before.

Technology always changes daily, and this is no different when talking about functional testing since they can now do more in one run. This means we will not need to do it repeatedly like before.

There are also a lot of new tools and software on the market for us to use, so be sure to check them out. When using functional testing, check them out first since they could save up much more time and energy.

These practices would surely help us with doing our jobs in testing a program/website. They are very effective and could save a lot of time for us since they work fast. It’s also important for us to keep our knowledge about how functional testing works so we can use it properly.


Functional testing is a vital part of software development because it’s the process that simulates how your application will perform in real-life scenarios. The goal is to identify any glitches, bugs, or other errors before it hits the market so you can make adjustments and prevent costly delays. Let me know your thoughts about functional testing in the comments section below.

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1 thought on “Functional Testing : Definition, Types & Examples”

  1. This tutorial on functional testing is nicely articulated. Functional testing has become a business imperative for any project, irrespective of its size. The risks of releasing a new software application without rigorous QA have greater implications now than ever before due to the rapid pace of change in demands and expectations of end users.


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