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Writer's pictureOngeziwe Bulana

Usability Testing vs Functional Testing: Do not confuse the two

When building a software you must keep these two testing approaches in mind Usability testing and functional testing these two approaches ensure that your application works as expected and provides a great user experience. Although they sound similar, these two tests address entirely different concepts. Lets explore their differences with a relatable example of a ‘notification’ feature.


What is functional testing?

Is a type of software testing that checks whether an application feature works as expected. It focuses only on the Technical functionality of the system and ensures that each feature performs according to the specifications requirements. 

The main goal of functional testing is to answer the question: "Does this feature work correctly?" 

For an example you have a notification button on your website. 

Functional testing would check if:

  • When clicked, does the notification panel open?

  • Does the button update to show the correct number of notifications?

  • Does it function properly on both desktop and mobile?

  • It behaves as expected across devices and browsers

Basically it ensures that the notification button functions correctly according to requirements. If all these checks pass, functional testing gives it the green light.


What is usability testing?

It is a method of evaluating how easy and intuitive a product or a feature is to a real user. It focuses on user experience (UX) to answer the question:

  • Is the feature intuitive

  • Is the feature function understood

  • Is the feature actually required

  • Would the average user understand its functionality

  • Can a user interact with this feature efficiently and enjoyably?

“Usability testing ensures that users can use the feature without confusion, frustration, or unnecessary effort.”


Here is where things get interesting. Lets say we have a feature where there is a notification bell icon that gets a red dot when a new notification is raised and for example the Notification icon/button works perfectly( thanks to functional testing)*** but**** it is tiny and it is hidden in the far corner of the webpage, making it hard for users to notice or click.

In usability testing participants might report that:

  • The user may be confused of what the "red dot” does or is meant to do.

  • The function was not evident enough on the page to draw attention.

  • It is too small for them to tap on mobile phone 

  • The location was not where the average user would expect it

Core principal difference between function and useability:

The feature is functional but poor usability makes it ineffective for users.


Key Differences 

Aspect
Functional testing
Usability testing

Focus

Behavior

User experience and satisfaction

Goal

Ensure the feature works as intended

Ensure the feature is intuitive and useful

Performed by

QA engineers or Testers

Real user or UX researchers

Example question

“Does the feature work?”

“Can users find and use the button easily?”

Why both are are critical

Let us return to the notification button example. Functional testing ensures that the feature works, while usability testing reveals whether users can benefit from it.

A button that functions perfectly but frustrates users due to poor design is a failure in usability testing. A perfectly designed button that does not work is a functional failure. Combining both testing types ensures your product is not only functional but also user- friendly. 


In conclusion, 

Think of functional testing as checking the engine of a car and usability testing as ensuring that the car is comfortable and easy to drive. Both are essential for a smooth ride.

Balancing these approaches ensures you deliver a product that works and delights users.


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