Functional Testing: Every Step Explained

    By Amy Montague, Thursday 12 December 2019

    There’s an old saying that “The first impression is the lasting impression,” and hence we, as digital businesses, always want our users to experience only the best of our end-products. If your product fails to deliver the first time, users will turn away and use competitor sites/apps. And thus here comes the role and purpose of functional testing.

    What is functional testing?

    Functional testing is the process which checks the functionality of a system against defined specific requirements. These functions are tested by providing input and examining the output. In simple terms, functional testing describes what a system does and how well it does it. Functional testing is vital as it verifies the quality of your system and if it is ready to be released to the public.

    This testing mainly involves black box testing, and it is not concerned about the source code of the application. The testing can be done either manually or using automation.

    What are the different types of functional testing?

    Firstly, let’s go through the different categories of functional testing.

    Different types of functional testing are:

    1. Unit testing: The purpose of unit testing is to validate each unit's designed performance. A unit is the smallest testable part of any software. It usually has one or a few inputs and usually a single output. Code coverage is an important part of unit testing, where the test cases need to exist to cover the below three:

    • Line coverage
    • Code path coverage
    • Method coverage

    2. Smoke testing: Smoke testing aims to ensure the most important functions of the system work. The result of this testing helps internal teams decide if a build is stable enough to proceed with further testing.

    3. Sanity testing: The main aim of sanity testing is to check that new functionalities or bugs have been fixed, before proceeding onto further development or launch stages. Sanity testing is a subset of regression testing and is usually performed when teams do not have enough time to perform more in-depth testing.

    4. Regression testing: This type of testing is used to confirm the stability of recent program or code changes which have not adversely affected existing features. Previously executed test cases are re-executed in order to verify the impact of possible change.

    5. Integration testing: Is a testing type in which one or two modules which are Unit tested are integrated into the test and verification is performed to ensure integrated modules work as expected.

    6. Beta/usability testing: In this type of testing, the final product is exposed to the actual customer in a production-like environment. The user's feedback is then categorised and addressed.

    What are the different steps that involve functional testing?

    Steps that involve functional testing:

    • The identification of functions that the software is expected to perform
    • The creation of input data based on the function's specifications
    • The determination of output based on the function's specifications
    • The execution of the test case
    • The comparison of actual and expected outputs
    • To check whether the application works as per the customer's need

    Why is functional testing important?

    Functional testing is important because it verifies the quality of a system and whether it is ready to be released to the public. During functional testing, a tester has to validate an application to see that all specified requirements of the client whatever have been mentioned in SRS or BRS has been incorporated or not. This type of testing is
    always concentrating on customer requirements, whereas non-functional testing is always concentrating on customer expectations.

    A functional tester holds a high-level of importance as the tester can analyse individual pieces of an application within the context of the entire application. The tester investigates an item, identifies integration points between that item and other parts of the application, and then formulates a strategy to inspect those weak points. Applications are usually weakest in places where different parts of the system come together. A strong functional tester knows how to exploit those weaknesses to identify any hidden bugs.

    In an organisation, functional testing will only be successful if the organisation’s underlying quality fundamentals are concrete and everyone vividly understands how testing helps achieve the goals of the business. Functional testing is only one of many activities that collectively comprise a comprehensive testing strategy. However, depending on the requirements and expectations of one’s company, different testing activities such as performance, load and security testing should be taken into consideration.

    Functional testing differs from other types of testing in the sense that it most closely reflects the experience of the users.


    To conclude, in functional testing, the functionality of the module is tested and the structure is not considered. It is performed based on a user’s perspective. This testing ensures that the system does what users are expecting it to do. And this type of testing means testing the functionality and checking the output as per the requirement documents.

    Want to start developing your functional testing? Talk to one of our Solution Consultants now or read more on our functional testing service page here

    (This article was written by one of our key community members, Manali Mehta, from India)

    Amy Montague

    Amy Montague

    As one of the Marketing Executives for Digivante, Amy provides and reviews most of the copy and visual content for Digivante. Amy has a natural flair for the creative and introduces aspect into her marketing role.

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