A test plan is a document that outlines the strategy and approach for testing a product or system. It includes details such as the scope of testing, objectives, resources needed, and the schedule. Test plans help ensure that all aspects of the product are evaluated and that any issues are identified before release. In software development, a test plan typically covers different types of testing, such as unit testing, integration testing, and user acceptance testing. By following a test plan, teams can systematically verify that the product meets its requirements and functions as intended, ultimately leading to higher quality and user satisfaction.