Functional Testing: A Complete Learning Guide

Featured Webinar: Simplify Compliance Workflows With New C/C++test 2024.2 & AI-Driven Automation Watch Now

Functional Testing

What Is Functional Testing?

As part of the QA process, functional testing is software testing that testers use to evaluate whether a system (or a component of a system) complies with the system’s (or component’s) purpose. Functional testing tests the operability of a piece of the entire system.

What Should Functional Testing Cover?

Minimally, DevOps should make sure functional testing covers the types of testing listed below.

Unit testing. Developers write test scripts that test whether each unit of the application matches the system’s functional requirements.
API (application programming interface) testing. Testers confirm that API responses and connections operate correctly. This includes how the connections handle user permissions and input data.
Smoke testing. Developers test the software after completion of each build in an effort to ensure that the software remains stable.
Sanity testing. Testers perform a simple assessment to determine if the “product” that the software produces is rational. This test usually follows smoke testing.
Regression testing. Testers use this test to ensure that any changes developers make to the base code, such as debugging strategies or new code, do not alter already existing functions or introduce instabilities.
Integration testing. In systems made up of multiple modules, this test ensures that the modules operate together correctly.
Usability testing. Real customers test the system as it operates in production. The objective is to determine how happy the customer is with the end product and to ascertain if the developers need to make any improvements.

Nonfunctional vs. Functional Testing

The difference between nonfunctional and functional testing is what they test. When testers employ functional testing methods, they ensure that an application’s features work correctly. Examples of functional testing include integration, unit, and API testing. With non-functional testing, testers test the performance of the application. Examples of this testing type include compliance, security, load, and accessibility testing.

Automating Functional Testing

In contrast to manual testing, with automated testing, testers use computers and software to run tests. Normally, testers write a Selenium script that specifies a series of testing steps. (Selenium is open source software.) In each step, the tester selects particular components of the UI (user interface) such as filling in a box, pushing a button, or selecting from a dropdown menu, and interacts with the components. Testers then ascertain the results and check them against what is supposed to occur.

A benefit of automated functional testing is the capability of running tests at any time day or night without the need to have a person continually involved. Automated tests also run faster than manual tests and they follow the testing plan exactly, avoiding potential human errors such as using incorrect test data or omitting part of the test. An added benefit is that automated testing gives the QA team more time to focus on urgent edge-cases and for writing test scenarios for new modules and software systems.

Want to develop a strategy and business case for test automation? Learn how to use ROI calculations to derive value in delivering high-quality software.

Download Strategy Guide

Benefits of Functional Testing

With functional testing, because it’s black box testing, the tester has no knowledge of the system’s logic. This helps prevent developer bias since the tester was not involved in developing the software and the expected output. Therefore, black box functional testing provides a more accurate test.

By contrast, white box testing, where testers test the “workings” of an application — the internal structures — requires that the tester has programming expertise and knowledge of the system’s logic.

Functional testing also doesn’t make any assumptions about system structure. It tests only on what comprises the system and what makes it work.

More benefits of functional testing include:

Ensuring that the developers have met all the product’s required specifications.
Ensuring the correct operation of the software product.
Creating a product that is free of defects, with the resulting improvement in software quality.
Ensuring safety and security.
Ensuring the end user or customer is happy.

Functional testing simulates people actually operating the system with real use cases. It helps ensure high code coverage and it checks to determine if the application or system is working on all platforms. It therefore ultimately proves that the system is working as it should, which thereby helps developers produce reliable, robust, and high-quality applications.

Talk to an Expert

Types of Functional Testing

In addition to those mentioned above, testers also employ the following types of functional testing.

System Testing

Testers test all of the components of the system for correctness and for compliance against the defined requirements. In other words, this black-box test validates the combined system. Testers perform the test before the acceptance test, using an almost real-life environment and usage.

User Experience Testing

This is a testing process testers employ to make sure that a website operates correctly when users interact with the various aspects of a website and its components.

Interface Testing

This testing checks the validity of data transfers and exchanges, and commands and calls between integrated components. More specifically, interface testing tests the communication between external components like the database, APIs, and web services and the application. This type of test often uses test automation and test automation tools enhanced with AI and ML to create and maintain UI and API test scenarios within the CI/CD pipeline.

Acceptance Testing

Testers perform this test after system testing the software application to make sure the end user is satisfied with the experience and that it fulfills all of the conditions stipulated in the business requirements. Acceptance testing provides the criterion as to whether the user accepts or rejects the software and whether the user releases it for use in the real world. Subcomponents of this black box test may include alpha testing, which skilled testers perform at the development site; beta testing, where testers employ real users at the client site; and regulation acceptance testing, which ensures the application complies with all legal and governmental requirements.

Explore Parasoft Solutions

Functional Testing Best Practices

Use Automated Testing

If testers are testing a specific function of the software repeatedly, they can write test cases for automation. These test repetitive, simple tasks thoroughly while providing the ability for testers to run numerous tests at one time to verify that a particular feature operates as expected. However, testers can’t automate all types of software testing. User acceptance testing, system testing, and exploratory testing require manual involvement to ferret out unusual bugs that user interactions may cause.

Use Exploratory Testing

Here testers investigate an application in an attempt to identify potential issues and bugs. This type of functional test is relatively unstructured: testers have the freedom to run tests when and how they see fit. The testing strictly focuses on how an application works, and testers can be QA personnel; they do not need to have training in languages like Java or Python. Testers test the entire app in real-world situations using real devices.

Test Often and Early

Working with agile methodology, developers need to catch problems with functions in the code or app early in the SDLC (software development lifecycle). This prevents any defects from having critical effects on the company or organization. When developers and testers test for functionality early and often, it can save the company money and pain by keeping bugs from reaching production.

Embrace Documentation

Documentation tracks issues through reports. Good reporting helps developers and testers understand the problems that exist and how and where to find them. Good reports also include the depth of test coverage, ordered steps on how to recreate problems, details about the severity and priority of issues, insights into what should occur when issues are resolved.

Use Well-Planned Test Execution

Test execution is when testers test specific workflows in an app. This allows testers to work through the exact functions of a web or mobile application systematically to make sure the functions work as they should within the workflow of the design.

Make Functional Testing Part of Your QA Approach

Functional testing is vital for creating workable, reliable software. When developers employ functional testing tools, the process reduces the number of bugs and issues and improves your customers’ experience.

Partner With Professionals

When you partner with Parasoft, you capitalize on our skill and experience, and simultaneously, free up your time so you can focus on test strategies and analysis and on developing new features and updates.

Example of Functional Testing

On a retail app, you want to be certain users can search for “men’s walking shoes” as an example. They should be able to click on the product that interests them, add it to their cart, and proceed to check out.

An example of functional testing of a retail transaction on a website. Lifestyle image showing a laptop displaying a transaction screen. A male's left hand is on the keyboard and right hand is holding a credit card.

Testers test each of these steps, including the search function, payment, and shopping cart, to determine if the app yields the expected results. The testers can report on whether the app conforms to the business requirements as written. If the app needs fixes or improvements, the development team can make the changes.

How to Get Started

To get started with functional testing, consult with your team to identify and locate the problems you’re having. Then reach out to Parasoft to present your concerns.

Parasoft can assign one of its experts to work with you. The first step in collaboration is to develop a plan for testing, including functional specifications, and ultimately resolve the issues your company is encountering.

Talk to an Expert Today

Why Parasoft?

Reduce the complexity and technical burden associated with testing by using an integrated and automated testing solution. The Parasoft Continuous Quality solution helps organizations succeed in their development efforts.

The Parasoft solution includes:

Complete test automation support for static analysis, unit testing, API testing, UI testing, security testing, and load/performance testing.
Reporting and intelligent analytics for immediate insights on coverage, compliance, and quality assurance.
Test data and environment management and simulation to streamline app testing.

Learn how our automated software testing platform can increase your application quality while meeting tight deadlines and budgets.

See Parasoft in Action