The Difference Between Functional and Non-Functional Testing

Every software development life cycle includes QA testing as one of the fundamental steps in building a great product. Various aspects of a software system are examined using different tests, which can be divided into functional and non-functional.

In this post, we'll discuss what makes test types different from each other. We discuss the types of functional and non-functional software testing that can be used to ensure project quality.

What is functional testing?

Functional testing specifies that the operation of a program or mobile application performs according to technical and business requirements.

Functional tests are usually performed before non-functional tests and are performed manually. The tester provides a specific input to the program and compares the result with the expected output. Functional testers don't care about source code, they focus on checking functionality.

In layman's terms, when you do functional testing, you are interested in what the system can do. Such testing is necessary to ensure that the product is free of any bugs or vulnerabilities.

What is non-functional testing?

Non-functional testing examines all aspects not covered by functional testing. It covers the performance, availability, scalability, and reliability of the software.

We perform non-functional testing to ensure that the interests of the end user are respected. If you can't meet customer expectations, the product will fail. Non-functional testing is essential to increase the market value of a product.

This type of testing requires more creativity from the tester. It has nothing to do with the mechanical work of the right click. Test specialists must develop strategies to gather customer expectations and provide a set of tests to verify how those expectations are met.

Results of non-functional tests are measured on a scale. If functional tests specify what a program should do, non-functional tests describe how it should behave. For example, how intuitive the user interface is or how well the system performs under heavy load.

Non-functional tests are usually automated. Dedicated tools help model real-world environments and see how the software behaves under preset conditions. Non-functional testing also relies on customer feedback and focus groups, especially when it comes to usability testing.

Functional testing VS non-functional testing: the difference between them

The easiest way to understand the area of ​​functional and non-functional testing is to look at some of the questions that help answer them.

Functional test questions

• Are confirmation emails sent after users register on the site?

• Will there be a feedback notification if the user uploads a larger file than the system requires?

• Will a new page load when the user clicks an icon that should be clickable?

Non-functional test questions

• How long does it take for a user to receive a registration confirmation email?

• Do feedback notifications conform to the user-friendly design principles of push notifications?

• Is it transparent to where the user clicks to load the new page?

Functional testing questions can often be answered with a simple “yes” or “no.” Non-functional tests give graded answers.

Which test type is better? The answer is no. They cannot be used interchangeably. Functional testing and non-functional testing cover different aspects of a software system and both should be used for quality assurance.

Functional testing types

You can use a variety of functional testing strategies to your advantage. The best way to ensure functional coverage is to use both manual and automated testing methods.

• Smoke testing is used before the actual test to ensure that the main function is working properly before other test procedures are fine-tuned.

• Sanity testing is performed after fixing bugs or adding features to check if this change hasn’t caused any problems.

• Unit testing is performed to check individual units or components of a system. Unit tests are typically automated and focus on verifying that specific functions or code segments work as intended in isolation.

• Integration testing is performed to verify the communication between various components of a system. These tests are essential to ensure that the different parts of the system work together as intended. Integration tests can be performed manually or automatically.

• Boundary value test is a black box testing technique that involves testing the software with input values at the edge of the defined acceptable range. This approach is used to find errors in software that occurs when values are out of range.

• API testing is a type of testing that focuses on verifying the functionality of an application's programming interface (API). API tests are usually performed using automation tools, although manual testing may also be used in some cases.

• User acceptance testing (UAT) ensures that software meets the business requirements of the user. UAT is typically performed by a group of users who are representative of the target audience. During user acceptance testing, these users engage with the software in a real-world environment to validate its functionality, usability, and overall suitability for their operational needs.

• Regression testing is software testing that verifies that a software system still meets the requirements after changes have been made. The purpose of regression testing is to ensure that the changes have not introduced any new defects into the system.

• Globalization testing ensures that the product will be available to users in other countries as organizations now aim to create goods that can compete in worldwide marketplaces.

• Interoperability testing validates that the program can communicate with other software systems and components without conflict.

• User interface testing is required to determine whether users will engage with the interface as planned. To carry it out, you must assemble an end-user group that will do certain activities. It aids in identifying the software parts that the user typically employs and if these elements behave following the requirements. It is critical not to mix up user interface testing with usability testing. User interface testing ensures that the interface functions properly, and that data is sent to the system. Usability testing is performed to determine whether end users will find the program helpful and convenient.

Non-functional testing types

There are many types of Non-Functional testing, some key ones are explained below:

• Availability testing is used to verify that a system is available to users when they need it. The purpose of availability testing is to ensure that the system can meet the required SLA (Service Level Agreement).

• Performance testing verifies the performance of the software application. The purpose of performance testing is to ensure that the system can meet the required performance levels.

• Compatibility testing checks how well the product interacts with other components such as the operating system, browsers, and hardware.

• Localization testing ensures that the product fits the requirements of a local audience. For example, if you want to localize a mobile app built for the US market and translate it into Chinese, you'll need to do this form of testing.

• Volume testing examines how effectively the system performs in the face of an increasing volume of processed data.

• Scalability testing is a software testing technique that establishes that the product can grow in proportion to the rising needs of end customers.

• Usability testing checks how user-friendly your program is.

• Reliability testing integrates stress, functional and security testing to determine whether the software product fulfils functionality criteria.

• Security testing is used to identify system flaws and establish how well sensitive data and internal resources are safeguarded. Security testing is crucial for assessing vulnerabilities and implementing measures to protect against potential threats, making it an integral part of a comprehensive software testing strategy.

• Load testing is about knowing how the program will react under a specific load. It is critical if you want to provide consumers with interoperable performance. Load testing allows you to evaluate the performance of your system under high peak loads.

• Endurance testing is used to assess a program's efficiency under large loads. However, the burden is constantly rising and lasts for an extended period.

• Compliance testing is a type of software testing which ensures that the product fulfils worldwide software development standards, which are often produced by multinational corporations. For example, a mobile application must comply with App Store or Google Play requirements.

• Stress testing is a type of performance testing. It examines how the software operates when subjected to varied loads and stresses on the app's functionality. Stress testing assesses the stability, resilience, and performance of a system under extreme or adverse conditions.

• Maintainability testing is critical for software to be able to securely go through modifications and upgrades. Maintainability testing determines how effectively a system adapts to changes.

• Portability testing defines how simple it is to move a software component or program from one hardware or operating system to another.

• Disaster recovery testing is used to assess how long it takes to recover and how successfully the program recovers data after crashes or network outages.

Summing up

Functional testing and Non-Functional testing are the two most important types that play a significant role in testing software. By including functional testing (such as unit tests, integration testing, user acceptance testing) into the equation of testing a software application, one can try what the process is up to and what the system does under any given circumstances. If Non-Functional testing is prioritized (such as load testing, security testing or localization testing), it deals with the system's performance and describes how the system performs under any given circumstances. Both have their pros and are limited to some constraints. It is completed, dependent on the user as to how he wants to test the system.