Reliability: The ability of the software product to perform its required functions under stated conditions for a specified period of time, or for a specified number of operations.
Reliability Testing: The process of testing to determine the reliability of a software product.
Usability Testing: Testing to determine the extent to which the software product is understood, easy to learn, easy to operate and attractive to the users under specified conditions.Basically Its a process of checking the user friendliness of a product/application.
Nov 18, 2013