Test control begins after the test plan is established, test control is an ongoing activity. A test manager will be able to effectively control test activities only if the testing schedule and monitoring framework has been established to track test work and resources against the plan.
In test control the actual progress is compared against the plan and the status of executing the plan including any deviation are reported. Test control guides the testing to fulfill the mission, strategies and objective including revisiting the test planing activities as needed.
Important point to remember in test controlling is the need to relate the status of test work products and activities to the test basis in such a manner which can be easily understood and relevant to project and business stakeholders.
Properly configured traceability matrix which has the ability to report on traceability status makes more complex relationships that exist between development work products, the test basis and the test work products more transparent and comprehensible.