UX researchers have developed many techniques over the years for testing and validating product hypothesis and particular design decisions. The methods range from well-known lab-based usability studies to those that have been more recently developed. In this article, we will explore seven different usability testing methods when you should use them and why.Before you pick a particular testing method, you should have a clear understanding of your target audience, available resources (time and money), and research objectives. This information not only will help you select the relevant testing method but also adjust the questions and tasks for your test participants:

• Guerilla testing is the simplest form of usability testing. Basically, guerrilla testing means going into a public place such as a coffee shop to ask people about your prototype. Test participants are chosen randomly.Guerilla testing works best in the early stages of the product development process.
• Unmoderated remote usability testing occurs remotely without a moderator. It offers quick, robust, and inexpensive user testing results to be used for further analysis. Test participants are asked to complete tasks in their own environment using their own devices and without a moderator present, which leads to the product being used naturally. The cost of unmoderated testing is lower; however, this type of testing offers less detailed testing results. Unmoderated remote usability testing works the best when you need to obtain a large sample to prove critical findings from your initial moderated research.
• Contextual inquiry is less a usability testing method and more like an interview/observation method that helps a product team obtain information about the user experience from the real users.This technique is useful for getting rich information about users— their workspace, personal preferences, and habits.
• Card sorting is an excellent method for prioritizing content and features in user interface. The technique is relatively simple—all you need to do is place concepts (content, features) on cards and allow test participants to manipulate the cards into groups and categories.Card sorting is great when you want to optimize your product’s information architecture.