Friday, June 2

What is Functional Testing, and why is it important? Types & Illustrations (Complete Tutorial)

In the simplest terms, functional testing verifies that an application, website, or system is performing as intended.

Each project begins with the creation of a document including functional or required specifications. Essentially, it lists the functions that the app/system/website should do from the user’s standpoint.

Functional Testing
Functional Testing

Functional Testing: What is it?

Functional testing is the technique through which quality assurance professionals verify whether a piece of software conforms to predefined criteria. It employs black-box testing methodologies, in which the tester is unaware of the underlying logic of the system. Functional testing is focused only on determining if a system operates as intended.

This article will provide an in-depth definition of functional testing, including its kinds, procedures, and examples, to help you understand its intricacies.

Functional Testing Techniques

  • Unit Testing: This is carried out by developers who construct scripts to verify that an application’s various components/units conform to the requirements. This is often accomplished by building tests that invoke the methods in each unit and verify that they return values that conform to the requirements.
  • Code coverage is required for unit testing. Ascertain the existence of test cases covering the following:
    • Line coverage
    • Code path coverage
    • Method coverage
  • Smoke Testing: This is performed after the release of each build to confirm that the program is stable and free of abnormalities.
  • Sanity Testing: Typically performed after smoke testing, this procedure verifies that an application’s primary functionality works flawlessly both alone and in conjunction with other aspects.
  • Regression Testing: This test verifies that changes to the codebase (new code, debugging tactics, etc.) do not disrupt or cause instability in existing functionality.
  • Integration Testing: When a system needs the operation of numerous functional modules, integration testing is performed to guarantee that the separate modules perform as intended when used in conjunction with one another. It verifies that the system’s end-to-end output complies with these essential requirements.
  • Beta/Usability Testing: Actual customers test the product in a production setting at this stage. This step is important to ascertain a customer’s level of comfort with the interface. Their input is used to develop the code further.

Functional Testing Workflow

A functional test is comprised of the following steps:

  • Establish input values
  • Conduct test cases
  • Compare actual and anticipated results

In general, functional testing entails the following steps:

  • Determine which product functionality should be evaluated. This may include testing primary functionality, messaging, error circumstances, and the product’s usability.
  • Generate input data for testing functionality by defined specifications.
  • Determine the output parameters that are acceptable in light of the established criteria.
  • Carry out test scenarios.
  • Contrast the test’s real result with the predefined output values. This indicates if the system is operating as planned.

For instance, a Use Case Scenario may be used to do functional testing.


A web-based human resource management system into which the user signs in using their user name and password. The login page has two text fields: one for the username and one for the password. Additionally, it has two buttons: Log in and Cancel.

When the login is successful, the user is sent to the HRMS main page. The cancel button terminates the login session.


1. The user-id field must have a minimum of six characters and a maximum of ten characters. These characters must be digits (0-9), letters (a-z, A-z), or special characters (only underscore, period, hyphen allowed). It is not permissible to leave it blank. The user id must begin with a numeric or alphanumeric character. It must not include any special characters.

2. The password field must have a minimum of six and a maximum of eight characters, including digits (0-9), letters (a-z, A-Z), and all special characters. It cannot be omitted.

The above use-case scenario may be validated using several functional testing methodologies.

1. End-user/system-level tests

Test the system to ensure that all components perform flawlessly together.

This would include testing the customer experience — loading the HRMS application, entering valid credentials, navigating to the home page, doing tasks, and logging out of the system. This test guarantees that the process runs smoothly and without mistakes.

2. Equivalence Assessments

The test data is partitioned into equivalence data cases. Each partition’s data must react identically in this test. As a result, just one condition has to be tested across all partitions. If a condition fails to function in one partition, it will fail to work in all subsequent partitions.

Because the user id field in the example may contain a maximum of ten characters, it should respond similarly if data more than ten is supplied.

3. Boundary Value Examinations

These tests are designed to determine how the system responds to the addition of data restrictions.

Since the user id must have a minimum of six characters in this example, this test will determine how the system reacts when fewer than six characters are input.

4. Tests with a decision-making component

These tests are conducted to determine what could happen to the system if a certain condition is satisfied.

The following decision-based tests may be conducted in this example:

  • If the user enters invalid credentials, the system should notify the user and refresh the login page.
  • If the user enters valid credentials, the system should redirect the user to the home page UI.
  • If the user enters valid credentials but wishes to cancel the login, the system should not redirect to the home page UI.
  • Rather than that, it should refresh the login screen.

5. Ad-hoc Examinations

These tests reveal inconsistencies that may have gone undetected by the previous testing. Ad-hoc tests are conducted with the intent of disrupting the system and observing its reaction.

For instance, an ad-hoc test may be performed to verify the following:

The administrator deletes a user’s account while the user is still signed in – and this occurs while the user is conducting activities. The test would determine if the program handled the situation appropriately.

Why Should Functional Tests Be Automated?

Automation may undoubtedly help minimize the time and effort required to conduct functional tests. Additionally, human error may be reduced, preventing defects from escaping the test step.

However, growing automation necessitates the development of test cases for each test by QAs. Naturally, developing the appropriate test case is critical to determine the appropriate automation tool for the job.

What should you look for in an automation tool?

  • The tool must be simple to use, particularly for all members of your quality assurance team.
  • It must operate effortlessly in a variety of contexts.
    • For instance, consider the following: Can you develop test scripts on one operating system and execute them on another? Are you looking for UI automation, CLI automation, mobile application automation, or a combination of the three?
  • It must-have features that are particular to your team’s needs.
    • For example, if some team members are unfamiliar with a certain programming language, the tool should facilitate conversion to another scripting language in which they are more comfortable. Similarly, if you want customized reporting and logging and automated build tests, the tool must support these.
  • If the user interface changes, the tool must allow the reusability of test cases.

Functional Testing Best Practices

  • Pick the appropriate test cases: It is critical to select the test cases to automate wisely. It is advisable not to automate tests that involve some setup and preparation during or before execution. Create automated tests for the following types of tests:
    • Tests that must be repeated
    • Simultaneous testing with distinct data
    • P1, P2 test scenarios that need a significant amount of time and effort
  • Subjective tests prone to human error
  • The same tests are performed on a variety of different operating systems, browsers, and devices.
  • Devoted Automation Team: Automation takes time, effort, and, most importantly, a specific level of specialized expertise and skill-set. Not every member of your QA team will be proficient at building automation scripts or using automation technologies. Before introducing automated tests, analyze your QAs’ ability and experience levels. It is ideal to assign automation jobs to individuals who are capable of completing them.
  • Reusable Data-Driven Tests: Automated test cases using numerous data sets should be created in a reusable manner. This may be accomplished by writing data to sources such as XML files, text, or property files or reading data from a database. By structuring automation data, the framework becomes simpler to manage. Additionally, it permits more efficient use of pre-existing test scripts.
  • Keep an eye out for test breaks: Your test cases and automation tool must react to any UI changes that occur. Consider an early version of Selenium that used a location to detect page items. If the user interface changes and those pieces are no longer in their original placements, test failures may occur across the board. Consider developing test cases that need little modification in the event of UI changes.
  • Test regularly: Create a simple automation test bucket and plan to be executed frequently. This enables QAs to strengthen the test automation infrastructure.

For more information regarding software testing such as Agile testing, you can also check our management section on our website by clicking here.

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