It depends on the scope of the project. Generally, user testing can involve a variety of approaches, depending on the size and scope of the project. For example, if the project is small and has a limited target audience, companies may ask people from the street and use online surveys to gather feedback. For larger projects, companies may use companies who specialize in UX testing services, or employ usability testing tools such as UsabilityHub, UserTesting, Silverback, and more. Ultimately, the approach chosen will depend on the budget and available resources.