Functional Testing: What is It, Types, Process, and More


Software development is a long process. There are many models to develop software. Modern SDLC models stress on doing testing as soon as possible.

Software testing is a rigorous process that involves various types of testing, including both automated testing and manual testing. In this article, we will discuss functional testing, its process, advantages, limitations, and types.

What is Functional Testing?

The system is tested against the functional requirements and specifications in functional testing. The purpose of functional testing is to ensure that the application meets the requirements or specifications.

This form of testing focuses on the outcome. It focuses on simulating actual system usage rather than developing assumptions about the system’s structure. It is a type of testing that confirms that each function of a software program meets the requirements and specifications. The source code of the application is unimportant in this type of testing.

The software application’s functionality is tested by supplying adequate test input, anticipating the result, and comparing the actual output to the expected output. The user interface, APIs, database, security, client or server application, and functionality of the application under test are all checked during this testing.

Types of Functional Testing

The following are the most popular types of functional testing:

1) Unit Testing

To ensure that each block of code/unit accomplishes its intended manipulation of inputs into desirable outputs for the next module, unit testing should begin at the beginning. Individual software units/components are tested to ensure that they work as expected.

2) Integration Testing

Multiple individual software units/components are tested as a group to confirm that the unit modules link as intended and transmit data and commands across the system according to the requirements built.

3) Smoke Testing

Smoke testing is a subset of test cases that tests the major/critical capabilities of the software in a non-comprehensive manner in order to guarantee that the product works well enough to move on to other tests.

4) Sanity Testing

Verify that minor code modifications and fixes do not have unexpected side effects in apparently different portions of the system after receiving a software build. If any such exists, then ensure that those defects have been fixed. If the build fails the sanity tests, it will be discarded to save time and money on more thorough testing.

5) Regression Testing

Check that further feature additions and bug fixes (due to code changes) do not have a negative impact on existing features. Regression testing is just a full or partial selection of previously conducted test cases that are re-run to confirm that current functionality is working properly.

6) User Acceptance Testing

User acceptance tests are the final step before software goes live, and they ensure that it can perform essential activities in real-world circumstances according to specifications. These tests are usually carried out by end-users throughout the Beta testing period.

What Advantages does Functional Testing Offer?

The following are some of the advantages of functional testing. It:

  • Guarantees that the consumer or end-user is happy.
  • Creates a flawless product/software.
  • Guarantees that all requirements are met.
  • Assures that all of the applications / software / functionalities of the products are working properly.
  • Guarantees that the software/product functions properly.
  • Ensures safety and security.
  • Increases the product’s quality.

Functional Testing Process Steps

A functional testing strategy usually goes like this:

Step – 1: Determine the Testing Objectives

According to the project requirements, functional testing goals are the features that the product should have. Validating that the program operates as expected and that mistakes and unexpected scenarios are handled gracefully are among the testing objectives.

Step – 2: Scenarios for Testing

Create a list of all conceivable (or at the very least the most significant) test scenarios for a certain feature. The different uses of the functionality are described in test scenarios. Multiple currencies, processing faulty or expired card numbers, and providing a notice on successful transaction completion are examples of test cases for a payment module.

Step – 3: Make a Test Dataset

Create test data based on the test scenarios you specified to emulate normal use settings. You can manually enter test data (for example, from an MS Excel spreadsheet or a printer) or have a script or test tool read and input data from a database, flat file, XML, or spreadsheet. Each item of input data should be accompanied by data that explain the desired outcome the data should produce.

Step 4 – Create Test Cases

Test case creation is an important part of software testing. Test cases, in the case of functional testing, depending on the various test inputs’ desired outcomes. If you submit an erroneous credit card number, for example, the program should give a clear error or warning.

Step 5 – Carry out the Test Cases

Run the test cases via the program and compare the results to what you expected. If the actual and expected outputs aren’t the same, the feature failed the test and a fault should be filed.

Step 6 – Deliberately seek out, track, and fix flaws

Once a defect has been detected, it should be entered into a formal tracking system that is available to the whole project team. Before marking a problem resolved, the necessary changes to the application should be done, and the test case should be run again to check the solution.

What is the Process of Using Automated Functional Testing Tools?

The user interface of the program under test can be interacted with by functional test automation tools. They can recognize screen objects like list boxes, text boxes, and buttons and make selections, enter data, and press them.

Many functional test automation solutions contain a recorder that ‘observes’ the user as they interact with an application and its objects on the screen, records the data they enter into the system, and records the actions the user takes, such as clicking buttons or selecting menus.

These actions can then be replayed to duplicate the user’s actions, using the objects, data, and actions captured during the recording. The testing tool records the results of these actions and compares them to the automation engineer’s predicted results to decide whether the test passed or failed.

Functional test automation engineers can build their tests step by step using the objects recognized by the tool, or they can start with a recording and customize the steps and parameterize the data to generalize it and enable tests to run in a variety of environments, including different browsers and mobile devices.

Limitations of Functional Testing

Functional testing focuses on how well an application accomplishes what it’s supposed to do, but it excludes other performance issues that aren’t directly related to the app’s functionalities but are nonetheless important to examine when deciding if it’s ready to go live.

Non-functional testing refers to evaluation and usability elements that do not fit within the functional testing umbrella. Examples include testing for:

  • Availability
  • Endurance
  • Ergonomics
  • Interoperability
  • Maintainability
  • Operational readiness
  • Recoverability
  • Security
  • Usability

Functional testing essentially encompasses the key components of an application’s design, ensuring that each function does what it’s supposed to do based on the application’s design and client or end-user requirements, but it neglects to account for other variables, such as how long specific functions take to execute, security, and other concerns that are equally important to most users.

While functional testing is an important part of the testing process, it does not guarantee that an application is suitable for production. Other downsides of functional testing, according to Software Testing Fundamentals, include the chance of missing logical problems in programs and the high likelihood of undertaking redundant testing.

Functional testing also necessitates a thorough understanding of user requirements, which aren’t always obvious or readily available, and creating context-specific tests to assess functional performance can be time-consuming.


Any software testing mechanism must include functional testing. It ensures that a system performs exactly as intended in real-time.

Because functional testing is done from the perspective of the user, it leads to the development of a high-quality product that satisfies the needs of customers and provides an excellent user experience simultaneously. Naturally, this simplifies the lives of both developers and business people.

Share Your Thoughts, Queries and Suggestions!