Functional Testing: The Complete Guide For Beginners

Software Testing is a very important stage in the Software Development Lifecycle to assure the quality of the software before releasing it to the market. It is responsible for detecting the potential defects and weaknesses in the product as much as possible.

Software testing is divided into two types:

  1. Functional Testing
  2. Non-functional Testing

Functional Testing is the type of testing that tests the functionalities of the software and checks ‘whether they meet the given requirements and specifications or not?’. It ensures that the software is good enough to fulfil the user’s needs. Since the testing process is not bothered by the internal structure of the software, so it is a kind of Black Box testing. 

In Black Box testing, the tester does not know’ how the software architecture has been designed?’ or ‘which algorithms are followed to write the source code?’. The only focus of the testing is to test the ability of the software to meet the predefined requirements and let the user perform the expected actions on it. It is done by giving a different type of input to the software and then comparing the generated results with expected results. The outcomes of these comparisons will evaluate the existence of any defect in functionality.

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What is the difference between Functional testing and Non-functional testing?

Functional TestingNon-functional Testing
It is done to test the operations of the software.It is done to test the performance of the software.
User’s requirements are the main focus of testing.User’s expectations are the main focus of the testing.
It is a kind of Black Box testing.It is a kind of Whitebox testing.
It tests the features available in the software.It tests ‘how the features accomplish their assigned tasks?’.

Once the development team is ensured that the software can meet all the given requirements, then, it is tested how efficiently the software is performing its operations. Hence, Functional testing is required to be carried out before non-functional testing.

Benefits of functional testing

1. This testing lets the development team enact the execution of the software just like it will be used in the real world. It is beneficial to find the bugs which a user might encounter while using the software in real-life scenarios.

2. It also doesn’t compromise with the testing of any requirement by using the internal structure of the software as an excuse.

3. Since, the software only passes the test when all the requirements are satisfied, hence the final product comes out to be a quality one.

4. It also helps in mitigating the possible risks to the software.

Functional Testing
Image Source: ProProfs

Types of Functional Testing

1. Unit Testing

The predefined test cases are performed by the developer over a module of code written by him recently, to test if it’s executing and the method calls are performing as intended.

It is responsible for maintaining the code coverage. The developer intends to execute each line of code at least one time.

It brings any error present in that unit to the notice of the developer, hence can be fixed at the same time, before moving forward.

2. Sanity Testing

Sanity test ensures that the software is meeting the main requirements it is developed to satisfy.

3. Smoke Testing

A smoke test is performed on every ready to release build, to test ‘if it’s stable enough to go live or not?’.

4. Regression Testing

A regression test is performed on the software after each defect in functionality is fixed to check if the correction is done has not led to a new defect in another component of the software.

It does not involve the testing of the whole software but only the functionalities that might have any impact due to the fix.

5. Integration Testing

In agile development methodology, where continuous integration and continuous deployment technique is followed, it is necessary to test if different modules written by different developers are individually working perfectly and are also compatible to work in coherence with each other.

6. User Acceptance Testing

The software is executed by enacting the user like environment to analyse the user experience while operating the software. It let the development team know ‘if the user can perform the actions easily or not?’.

Functional Testing lifecycle
Image Source: SIMFORM

Also, read Best Free Web Load Testing Tools To Try In 2021.

How to perform Functional Testing?

There are the following stages involved in the software functional testing:

1. First of all, the major functionalities of the software are determined which have to be tested for the existence of any error. 

2. Then, the input data is selected that will be fed to the software to check ‘if it meets specified requirements or not?’. 

3. After this, the expected outputs for the inputs created for functionality in the last stage are stored.

4. Now, it’s time to execute the created test cases.

5. At last, the generated outputs are compared with the expected output for input to the functionality. If the outputs come out to be the same, then the functionality is working as desired, else need some corrections.

Functional Testing tools
Image Source: G C Reddy

Functional Testing Tools

1. SmartBear

SmartBear provides a set of tools for testing the functionality of a software. It helps in reducing the development team’s efforts and time required to test the software without compromising the quality of the product. SmartBear helps in increasing the effectiveness of Manual Testing.

2. CrossBrowser Testing

CrossBrowser Testing allows the tester to test the software interactively. It helps in making exploratory testing more effective. Even the software can be executed on various platforms which are different combinations of operating systems, browsers and devices, to check ‘if users on the different platform will have the same experience while operating the software or not?’.

3. Swagger Inspector

Swagger Inspector provides its services to test any API, free of cost. All you need to do is paste your URL on its website to test the and generate the documentation of the API. It also does not require any setup or download.


Functional testing is the one that validates ‘if the software is fulfilling the user’s and client’s requirements and specifications, it is developed for.

Because in the end, there is no use of a large amount of program and effort, if the software doesn’t perform the functionalities it is expected to. It is a major reputation issue of any enterprise. There are a large number of techniques and tools available which can help in releasing a bug-free software ensuring quality user experience.