Usability testing is a technique for ensuring that the intended users of a system can carry out the intended tasks efficiently, effectively and satisfactorily. Usability testing it is carried out pre-release so that any significant issues identified can be addressed. Usability testing can be carried out at various stages of the design process. In the early stages, however, techniques such as walkthroughs are often more appropriate. The objective of usability activities at the implementation stage are to ensure that detailed design takes account of usability principles.

This can be achieved by:

use of style guides and design guidelines •
ensuring that rapid prototyping activities incorporate usability •

The purpose of testing and measuring is to assess the degree to which user and organizational requirements have been achieved, and to provide feedback in a form that can be used by designers and developers to improve the user interface design. There are a number of different evaluation methods that vary in terms of formality, rigidity and the degree of user participation. The most suitable method will depend on the product being developed, the availability of representative users and financial/time restrictions. Evaluation can be user based or expert based. User based testing will provide information related to the task at hand - does this design support the user in their work. Expert inspections tend to identify lack of conformity to standards, interface design guidelines and expert comments based on experience.