When an interactive product or system has been built, there typically is a final phase of 'user acceptance testing'. This is to ensure that the product complies with functional and quality requirements, including usability.
This should not be the first time the design is evaluated for usability! Iterative design & evaluation help ensure that you get things right during design, and that acceptance testing gives no nasty surprises.
By the acceptance stage it is difficult and costly to make major changes. But it is essential to identify any critical problems, and assess their likely impact on the product's success. Late evaluation may also help identify quick wins - minor changes that make a big difference to the quality of use.
Pilot release or phased release is strongly recommended:
- try out the product on a limited number of users
- make essential changes & quick wins before full release.
Once the product is released, user feedback and evaluation are important to
help incorporate improvements in future versions. This may involve:
- direct user feedback
- usage monitoring
- post-release user surveys
When a further release is being planned, consider doing some further formal
user testing of the existing product.