Test strategy is a higher level document defining "How to test". However; Test Plan defines "What to Test".
Test strategy defines how different functionalities will be tested and testing tools to be used. Also, it provides test cases designing methodology that will be used. But test plan defines; features to be tested (In -scope), features not to be tested (Out scope), risk analysis, entry and exit criteria, Roles and responsibilities of each and every team member and Project Schedule It is a set of guide lines that describes test design. Test strategy says - How testing is going to be performed? What will be the test architecture? Test Strategy Document describes what we are going to test and what all are the testing approach to be followed by the Test Engineer.
Test strategy defines how different functionalities will be tested and testing tools to be used. Also, it provides test cases designing methodology that will be used. But test plan defines; features to be tested (In -scope), features not to be tested (Out scope), risk analysis, entry and exit criteria, Roles and responsibilities of each and every team member and Project Schedule It is a set of guide lines that describes test design. Test strategy says - How testing is going to be performed? What will be the test architecture? Test Strategy Document describes what we are going to test and what all are the testing approach to be followed by the Test Engineer.