The software test plan (STP) is designed to prescribe the scope approach resources and schedule of testing activity.
The plan must identify the item to be tested, features to be tested and type of testing to be performed.
Better test cases have more reliable results, improves performance of the system as well as lowering cost in three categories, (1) Productivity - less time to write and maintain cases (2) Testability - less time to execute them.
(3)Scheduling reliability- better reliability in estimates [4].