A document describing the scope, approach, resources, and schedule of intended test activities. [ IEEE 1012, ISO/IEC 12207, ISO/IEC 15939 ]
Test Plan [ IEEE 1012 ]: A document that describes the technical and management approach to be followed for testing a system or component.
Test Plan [ ISO/IEC 2382 ]: A plan that establishes detailed requirements, criteria, general methodology, responsibilities, and general planning for test and evaluation of a system.