The ISTQB® defines a test plan as a list of activities, tasks or events of the test process, indicating their planned start and end dates and their interdependencies.
A test plan is therefore a document that describes in detail how a software or system test is to be carried out. It includes objectives, resources, schedule, test scope, test methods, test cases and responsibilities to ensure that the quality and functionality of a product can be tested and evaluated. The test plan helps to organize the test process and ensure that the requirements are met.