What is usability testing?

Usability testing, or user testing, is the most effective method for evaluating software, a website, or an app. The test consists of directly observing the user’s journey using the product to allow concrete identification of problems. Usability can be measured by calculating the user’s performance.

The usability test is an opportunity to see the user in a situation and to observe the problems they encounter, the questions they ask, and the functionalities they like or dislike. Development teams thus gather valuable insights on how to make the software more enjoyable to use.

Why is usability testing important?

  • Observe the user in a real context of use.
  • Verify whether or not the product meets the user’s expectations.
  • Identify the problems encountered by users.
  • Reduce the risk of building the wrong product.

How many users are needed for the test?

5 users can be enough:

  • J. Nielsen has shown that tests conducted with 5 users can remove at least 80% of usability problems. By increasing the number of users, you don’t find more problems.
  • Testing with more users increases the cost of the test, not the relevance of the results. Rather than testing with 15 users, J. Nielsen* considers that it is better to do 3 tests with 5 users, improving the interface with each iteration.
  • Of course, when the application targets different types of users, it is important to test with different groups.

How to measure results?

Measuring usability consists of carrying out 3 types of measurements :

Effectiveness: Verify that the objectives targeted by the user are achieved.

Efficiency: Measuring the resources needed to achieve these objectives, such as the time taken by the user to complete the task.

Satisfaction: Determine if the system is pleasant to use, for example by counting the number of negative comments made by users during the test.

Depending on the application, it may be useful to assess other aspects:

Security: Number of errors made by the user and speed of error correction.

Ease of learning: Correct understanding and quick assimilation of the operating mode.

Important point:

During the test, it happens that the user does not dare to say that he does not succeed in using the software or the website. He prefers to hide his difficulties, rendering the test results null and void. It is essential to give the user confidence at the beginning of the session by reminding them that :

  • The purpose of the test is to evaluate the software, not the user.
  • The user fails to use the software because the software was poorly designed.
  • The purpose of the test is to identify usability problems with the application, not to measure the user’s ability to use the software or website.

*Jakob Nielsen: (born 5 October 1957) is a Danish web usability consultant. He holds a Ph.D. in human-computer interaction from the Technical University of Denmark in Copenhagen. Dr. Nielsen established the “discount usability engineering” movement for fast and cheap improvements of user interfaces and has invented several usability methods, including heuristic evaluation. He holds 79 United States patents, mainly on ways of making the Internet easier to use.