Testing a product to ensure it meets the user's expectations is one of the core principle of User Centered Design (UCD). Here are the 4 main types of usability tests that you could run:
Concurrent Think Aloud (CTA) is used to understand participants’ thoughts as they interact with a product by having them think aloud while they work. The goal is to encourage participants to keep a running stream of consciousness as they work.
In Retrospective Think Aloud (RTA), the moderator asks participants to retrace their steps when the session is complete. Often participants watch a video replay of their actions, which may or may not contain eye-gaze patterns.
Concurrent Probing (CP) requires that as participants work on tasks—when they say something interesting or do something unique, the researcher asks follow-up questions.
Retrospective Probing (RP) requires waiting until the session is complete and then asking questions about the participant’s thoughts and actions. Researchers often use RP in conjunction with other methods—as the participant makes comments or actions, the researcher takes notes and follows up with additional questions at the end of the session.