What is Functional Testing in Software Testing? [Definition Types + Examples]

What is Functional Testing?

Functional Testing is a type of software testing that allows you to validate software works according to specified functional requirements. With the functional testing process, you can focus on the business requirements and the software’s behaviour to ensure that it behaves as expected under different conditions.

Functions tested can include user interface interactions, databases, client/server communication, and operational procedures within the software. However, software testing is divided into functional testing and non-functional testing. Functional testing is primarily conducted and then non-functional testing is done. Moreover, both types of testing are important when you want to release an error-free solution. When you are performing functional testing of your software, you should also perform non-functional testing as well. You must check our guide on software testing types before you conduct software testing.

The primary goal of functional testing is to ensure your software performs as expected from functionality aspects. If your software is not performing, you need to fix issues. By doing so, you enhance the software’s quality, ensure its usability, and reduce the risk of functional failures after deployment.

The Scope of Functional Testing

Here is the list of scopes where you can perform the functional testing.

• User interface (UI): One aspect functional testing covers is assuring that the software’s UI behaves as expected. In user interface testing, you check all the buttons, links, forms, menus, and other interface elements.
• Database: Functional testing also involves validating the software’s interactions with the database. That means you check if the software properly stores, retrieves, and deletes data as necessary.
• APIs and integrations: If your software integrates with other software or uses APIs, functional testing verifies that these connections work smoothly.

Types of Functional Testing

Here are the core types of functional tests. Learn about each in brief.

• Unit testing: In this type of functional testing, you check all the individual and isolated software components (units) are working properly.
• Integration testing: In this testing type, you check the interaction between different software modules after they have been unit tested.
• System testing: System testing validates the complete software to ensure it meets the specified requirements.
• Regression Testing:This type of testing is performed after any modification or updates in the software to ensure that the changes haven’t adversely affected existing functionalities. Check our brief explanation of regression testing to learn more about it.
• Acceptance testing: User acceptance testing (UAT) helps you to verify if the software meets the end user’s requirements and expectations.

Short Brief on the Process of Functional Testing

Understanding the process involved in functional testing can provide you with better insights. Let’s learn about the process in a simple context.

• Identify functions: The first step is to identify the functions that the software is expected to perform, as outlined in your requirements document.
• Create input data: Next, create appropriate and varied input data for each function based on your identified test cases.
• Determine output: For every set of input test data, determine what the expected output should be according to your specifications.
• Execute test cases: With the help of functional testing tools, now you run the test cases by feeding the input data into the software and recording the actual output.
• Compare and analyze: The final step involves comparing the actual and expected outputs and analyzing any discrepancies to rectify errors.

Importance of Functional Testing

Let’s learn about the benefits when you perform functional testing.

• Quality assurance: The most obvious benefit is ensuring software quality. It can help you identify and address issues before your software goes live, thereby preventing future complications and end-user dissatisfaction.
• Better user experience: By thoroughly testing all the functional aspects of the software, you enhance user experience, as all elements will work as intended.
• Business reliability: In an increasingly digital world, software functionality directly affects a business’s reputation. Functional testing ensures that your software delivers reliable performance, reinforcing your business’s credibility.
• Cost-effective: Catching bugs early in the development cycle is cheaper than fixing them post-release. Functional testing can thus contribute to cost-effectiveness.

Examples of Functional Testing

Let’s check the examples of functional testing which includes unit testing, regression testing, usability testing, white-box testing, and black-box testing techniques as well. Here are the practical examples of testing which are explained at a core level executed during software development.

1. Login functionality: Consider social media software. One of the most basic functions that users perform is logging into their accounts. Check the following section to learn how functional testing is done at an individual level.
   • If you enter the correct username and password, you should successfully log in.
   • If you enter an incorrect username and/or password, your access should be denied. An error message indicating unsuccessful login should appear.
   • If you attempt to submit the form with an empty username and/or password field, you should not be allowed to proceed. A validation message should appear instructing you to fill in the required fields.
2. Search functionality: Suppose you are testing a search engine website. The functionality to test here is the search operation.
   • When you enter a keyword in the search box and press the search button, the software should display results that are relevant to your search query.
   • If you leave the search box empty and press the search button, the software should respond with an appropriate prompt or display a list of trending topics.
   • As you begin to type in the search box, the auto-suggest feature should proactively provide you with related search suggestions.
3. Shopping cart functionality: If you’re testing an e-commerce website, the shopping cart is a critical feature. Check how functional testing is done when different components are combined.
   • When you add a product to the cart, the product should be visibly added to your shopping cart.
   • If you choose to remove a product from the cart, that product should immediately disappear from your cart.
   • If you change the quantity of a product in your cart, the total price displayed in your cart should update accordingly to reflect this change.
   • When you proceed to checkout with items in your cart, you should be smoothly directed to the payment process to complete your purchase.
   • However, if you attempt to checkout with an empty cart, a message should appear on your screen indicating that your cart is empty and that you must add items before proceeding to checkout.
4. Form submission: If your software includes a contact form, functional testing should ensure that it works as intended. Here is a brief explanation.
   • When you fill out all the fields correctly in the form and submit it, the form should be successfully submitted, and you should be able to see a success message indicating the same.
   • If you attempt to submit the form with one or more mandatory fields left empty, the form should not be submitted. Instead, you should see a validation error prompting you to complete all required fields.
   • Every input field in the form should have its own validation. If the input provided in a particular field doesn’t match the required format, an error message should appear to guide you in providing the correct input.

These are examples of functional testing for a particular software. Now, functional testing would involve a similar approach to all the functionalities of the software, ensuring that they behave as expected under various conditions.

In conclusion, functional testing is a cornerstone of quality assurance that verifies the functionality of the software. By understanding its role and significance in your software development lifecycle, you can effectively leverage it to enhance your software quality and end-user satisfaction. Remember, well-functioning software is the first step toward a satisfied customer.