Its main task is evaluating if the system or peripheral is easily used by the user In order to reach this objective, factors such as the disposition of elements on screen, colors, points of attention, text clarity, learning and relearning (intuitive system) are taken into consideration.

Moreover, Zero-Defect works with the Usability Engineering model - according to ISO 13407: Human Centered Design - so that the system or peripheral is developed according to the using expectations of the user speeding the process of software approval.

Along with the Usability Test, Interface Test is carried out, with the objective of evaluating the elements the user interacts with for input of data and its corresponding output. This test is generally carried out with the Functional test, which can be also performed in an automated way in a joint process.

Common services that apply this test: System Approval, Web Systems Validation, Validation of Systems in Evolving Maintenance.