Testing plays a very important role in the development of an application. It lets the developer know the potential issues and errors, so that he can code accordingly and make the application work perfectly.It is very important to satisfy the customers for whom the application is being developed.So it is vital to test the application by interacting with it in a user perspective.This type of testing where the application is tested on how the users interact with it is called "Usability Testing".

Before starting to develop an application, we must know how the users will interact with it so that the developer will know the potential issues before hand and he can code accordingly to develop a user friendly and stable site. If we release an application to the customers without performing usability testing ,then it will be overwhelming for the application and the developer by the different unusual interactions of the users with the application.This will lead to errors in the application making the customers unhappy. So it is better to know before hand how the users will use the application and develop and test accordingly.

                           

During a test, participants try to complete specific tasks  while observers watch, listen and takes notes because the goal of usability testing is to identify usability problems.So to run an effective test , we have to first develop a test plan,recruit required number of participants and then analyse and report our findings.Usability testing lets the design and development teams identify problems before they are coded.Therefore it saves development time and cost. 

Usability testing lets us learn if participants are able to complete specified tasks successfully and how long it takes to complete specific tasks.It helps us know how satisfied the participants are with the application and if there are any changes required to meet the usability objectives. The more the application is user friendly,the more the users will enjoy their interaction and much more likely to recommend it to others. Examples of products that commonly benefit from usability testing are consumer products, web sites or web applications, computer interfaces,etc.

References

http://www.hongkiat.com/blog/usability-testing-what-you-need-to-know/

http://www.usability.gov/how-to-and-tools/methods/usability-testing.html