Usability testing is the method of testing something by using and seeing the particular product. That is the users are made to complete some measured tasks with the product, they will be observed at the same time by the researcher. The product quality is evaluated by the researcher while being used by the user. Normally the usability testing evaluates the ease of use. That is how easy the particular product is to use by the normal user. This type of testing has the huge part in defining the success of the product after launch.
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The usability testing includes several types including Comparative Usability Testing, Explorative Usability Testing, etc. Before launching a product, many flaws are identified with the help of the usability testing and made more convenient for the users to use the product. Usability testing minimizes the risk of the product failure. It visualizes the likelihood of the usage and hence product improvements can be done before launching. Usability testing is purely based on the qualitative testing and hence helps the developers/owners to rectify the flaws and launch the 100% complete product for the users to use with. Ultimately, the usability testing is must for all the applications/products before launching.