In Early days, most of the design teams waited until the end of the production to test. They referred this as '' Validation''. Designers in those days equated success in the usability test with success in the design.
If you are almost certain to find serious problems in the product and you wait until the end to do the test, then you have the frustration of neither time or resources to fix the problem.
This type of end-of-process testing has a legitimate place in the usability specialist toolkit. However, it should not be the considered as the only usability testing. Why not? - To complete design process free of problem, the problem need to be fixed during the process testing which product is planned, designed and developed is called 'Formative Testing'.
The goal of formative testing is to find the critical problems that prevents users from completing task. You want to learn about your design's problems during the usability test, formative test is the way to achieve success by finding and fixing problems early.
Five Tips to Successful User Testing :-
1) Start Early - When the problem is found in the design process you save time and money.
2) Select the issues those have controversial problems. These type of problems can be solved easily.
3) Find participants who really represents users you are concerned about if what you learn is not visible developers may not act accordingly.
4) Watch and listen carefully. Detect not only the problems but their cause as well.
5) Motivate the designers and developers to work and make them realize that uncovering problems is not a sign of failure.
Success in usability test is learning what is working well and what is not. It is important to record the positives and the problem as well. After the test, communicate the results with the team as if the team members do not understand what is the problem, how it should affect the outcome, they won't make necessary changes. A successful usability test results in design improvement.
Focusing on formative test is the secret to successful usability test.