Difference Between Functional and Non-Functional Testing

High-quality software delivery is essential to boost your customer experience and keep them coming back for more. Two approaches that help you in this regard are functional testing and non-functional testing. 

The purpose of both testing types is to ensure the software meets the highest quality standards and works as expected. However, before the practical application, it’s important to first understand the core concept of these testing methods and how they differentiate from each other. 

This article is your complete guide to functional vs. non-functional testing, their similarities, differences, and much more. Let’s begin! 

What is Functional Testing?

Functional testing is a type of black box testing strategy that checks the functionalities and capabilities of a software solution based on factors like software input and output, user interactions, and data manipulation. It validates system interaction with software components and verifies whether the system is working according to the set requirements and intended business needs. 

Advantages of Functional Testing

The advantages of functional testing are numerous, including the fact that the software works as per business requirements and is free from all types of bugs. Let’s discuss these points in detail:

• Makes Sure Software Works as Expected 

For every software, the developers first lay out a plan and set of instructions that the end product must meet. Any deviation from these may lead to faults in the software that impact user experience. 

This is where functional testing comes in! It covers all the functional aspects of the software, including API interactions and all application key features. 

You can run these tests to check whether the software is able to perform as expected. If there are any issues, the development team can fix them before deploying them to the production environment, improving software quality. 

• Allows Quick Bug Detection

Bugs are common in software development. However, undetected bugs, be they security bugs or functional bugs, not only lead to costly fixes down the road but also impact user experience. 

One of the benefits of functional testing is that it allows for quick bug detection. You can pinpoint issues early in the development cycle, like problems with data validation or the improper working of form submit buttons. 

This prevents any roadblocks later in development and also prevents you from falling victim to expensive post-release fixes. 

• Quick Time-to-Market 

To stay relevant and at the top of your customer’s minds, you have to deliver products quickly to the market. Functional testing is a great help in this! 

It rigorously verifies all the functional elements of the software and also detects issues early on, eliminating delays that may arise after deployment. 

You can also use some automated functional testing tools to streamline the whole software testing process. This significantly lowers testing cycles and paves the way for faster releases, which is important to cater to changing market demand. 

What is Non-Functional Testing?

Typically, non-functional testing is a broad term that covers all the non-functional aspects of software. It tells you how the software performs under certain conditions and focuses on checking its user interface intuitiveness, stability, reliability, and overall performance. 

Advantages of Non-Functional Testing

The major benefits of non-functional testing range from enhanced user experience to robust security and reliability. Here’s a detailed explanation of all these benefits:

• Improved Software Performance 

One of the key benefits of non-functional testing is that it checks the overall performance of the software. 

For instance, it may evaluate the load capacity of the application by simulating an environment with multiple users. It can also measure response times under different stress conditions. 

This allows developers to identify and fix lags or bottlenecks that may compromise user experience, ensuring the application runs smoothly all the time. 

• Helps Ensure High Security 

Did you know that small businesses account for 43% of cyber attacks yearly, and 46% of cyber attacks are on small businesses with 1,000 or fewer employees?

To avoid this, you should produce highly secure software solutions, and non-functional testing ensures this. It lets you check the system for any vulnerabilities and weak points that may expose it to security threats. For example, you may run penetration testing to uncover potential exploits that are harmful to your business reputation. 

Based on the findings, your software development team can then implement robust security controls like two-factor authentication or encryption. Hence, your critical business and customer data stays safe, boosting customer’s trust in your services. 

• Enhance Software User-Friendliness

Your software solution should be user-friendly so that customers feel satisfied and return for more. Another benefit of non-functional testing is that it evaluates the application’s usability. It ensures that the software is easy to navigate and functions well across all browsers, resulting in high customer satisfaction and retention. 

Key Differences Between Functional and Non-functional Testing

Functional testing makes sure the code and software infrastructure you’ve built are working perfectly, while non-functional testing validates that the software is following the right way to perform certain tasks. They have a few similarities; however, their major difference lies in the following:

1. Execution 

• Functional Testing: It checks if the software with all its functionalities works as expected. 
• Non-Functional Testing: The execution of non-functional testing is to assess how the software performs under various conditions. 

2. Focus area – what is tested? 

• Functional Testing: Functional testing targets specific features and functionalities, such as user authentication, data validation, form submission, and more. 
• Non-Functional Testing: This testing examines non-functional aspects like scalability, reliability, and security of the software. 

3. Objective 

• Functional Testing: Its main objective is to ensure that the designed software meets the set requirements and criteria provided and decided by all stakeholders. 
• Non-Functional Testing: Non-functional testing aims to validate that the software offers top-notch performance and user experience. 

4. When to perform 

• Functional Testing: Well, functional testing can be conducted at any stage of the development cycle. 
• Non-Functional Testing: On the other hand, non-functional testing is typically performed after functional testing. 

5. Requirements 

• Functional Requirements: Functional testing is performed based on a pre-defined set of instructions and expectations. 
• Non-Functional Requirements: However, to do non-functional testing, you require performance metrics like response time, CPU utilization, and latency. You also need to think from a user perspective and test the software, simulating real-world scenarios. 

6. Automation Potential 

• Functional Testing: It can be easily performed manually, but you can also rely on some automation tools. 
• Non-Functional Testing: Non-functional testing has huge automation potential as it is not easy to perform manually. 

7. Tasks 

• Functional Testing: Functional testing involves a wide range of tasks, including validating user interactions like logging into their accounts, correct data processing, and displaying appropriate error messages. 
• Non-Functional Testing: Non-functional testing measures system performance under conditions like excessive load or security breaches. 

8. Testing Techniques/Types 

• Functional Testing: Types of functional testing include integration testing, regression testing, unit testing, and user acceptance testing. 
• Non-Functional Testing: Non-functional types of testing include security testing, load testing, usability testing, stress testing, volume testing, performance testing, and scalability testing. 

9. Tools 

• Functional Testing: Functional testing tools include Selenium, Appium, and TestComplete. 
• Non-Functional Testing: Non-functional testing tools include TestRail, Loadster, and Apache JMeter. 

10. Example Test Case

• Example of Functional Testing: Verify that the user can open the contact information form. 
• Example of Non-Functional Testing: Measure response time for the payment function under peak load. 

Why Both Functional and Non-functional Tests Are Essential in Software Development?

Although there are some differences between functional and non-functional testing, both are critical to the success of your software application. 

Both these methods complement each other and integrate smoothly into your CI/CD pipeline, helping you save money by identifying potential bugs early in the development cycle. 

Not only this, but they also enable you to deliver high-quality software solutions to customers that are highly reliable, optimized for all devices, and offer fast response times. Customers feel satisfied with your services and tend to become your loyal prospects, leading to high revenue. 

Functional and non-functional testing is your key to outshining your competitors and becoming industry leaders. Nonetheless, if these concepts seem like a lot to take in, contact us. Our expert developers help you design and deliver excellent software solutions free of all types of bugs, paving the way for business success.