Usability Testing or Functional Testing first?

Functional Testing VS Usability Testing

In the recent years, we can see the booming of number of apps in the market, hence the increase of startup company as well. In Google Playstore alone, as of 1st December 2017, there are 3,517,998 apps available* to download!

Before I started Bugs Detective, I’ve been working with various organisations from small to multinational company. I’m also working as freelance test consultant. Based on my experiences, I got a lot of questions either should I invest in functional testing or usability testing as well. I can also say, at least in Malaysia, most companies are too concern and invest more on usability rather than functional testing itself.

Don’t get me wrong but yes, usability is very important because without usability research and testing, users might abandon the app, but get this, there’s no use on investing heavily on usability while the apps doesn’t work at all due to lack of functional testing done thoroughly and correctly.

Functional Testing and Usability Testing needs to be done correctly in order for your app to perform well ultimately! Essentially, functional testing need to be done first before you proceed with usability testing. Before I go further, Lets understand what is functional testing and usability testing first.

Functional Testing

Functional Testing basic

Functional Testing basically is a testing designed to ensure that the functional requirement are met. It’s derived from use cases/your app requirements. In other words, Functional testing is to ensure that your app working as expected based on functional specs/requirements document. It can be manual or automated.

Functional Testing consist of (this is just a basic, there’s more to it):

  • Unit Testing
  • System Integration Testing (SIT)
  • User Acceptance Test (UAT)

Usability Testing

Usability Testing is basically to test the ease of use of the app. The functionality works, but how easy is it for the functionality to work from user’s perspective. Usability testing is a part of Non-Functional Testing. There are others as well such as performance testing, load testing, soak testing etc, but in this post, I’m going to focus on Usability Testing alone. Normally, Usability Testing will be done by users doing certain business process on your app together with a survey or questionnaire. E.g. On the scale 1-5, how easy for you to purchase this? Does it take long to load etc. With the outcome of usability testing, you may decide to go for performance testing etc.

Let’s take this example below:

Scenario 1:

User should be able to make a purchase successfully.

Effectively, for functional testing, you will start by unit testing that is done by developers followed by System Integration Testing and so on. Testers will test every single unit and the integration from one unit to another unit as well (End to End).

Functional End to End Testing

Testers will start the testing from user registration page end to end. Within one page itself, they will be several testing including negative testing as well. Normally, they will be a structured test cases for that.

As for Usability Testing, users or testers will complete the business process and the goal is the usability of the app itself. The ease of use etc. As per same scenarios above, the testers will normally see on how easy for them to make the purchase. Are there any unnecessary steps that they need to do, does it take too long to load to another page etc and essentially they will then answer the survey based on the activities they did.

Usability Testing Sample

Functional testing and Usability testing basically compliments each other. There’s no use on investing heavily on Usability but once you release your app, users found a big functional issue and give a bad review to your app. At the same time, if your app works perfectly but gives a bad users experience, it will also impact your review and number of users as well. What I’m trying to say is, thorough testing play a major role for your app and for your company as well. With good development and testing practices, it will increase the reliability of your apps, increase your app rating, hence, increase your sales!

If you would like to know about perfect testing solutions for your app and how we can help to improve the quality of your app, please contact We would be very happy to assist you. We’re also offering a FREE 1 test cycle for your app, so that you can see the impact and differences with and without thorough testing.


Kamil Khaidir Roslan
Author: Kamil Khaidir RoslanWebsite:
Principal Consultant & Co-Founder of Bugs Detective
A passionate software tester with extensive experience in software testing. Involved in various type of testing with various type of clients, locally and globally and also involved in giving training on software testing methodology and enterprise tools.

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