A system test planning is the first thing that should happen in software testing. System test plans outline the process of testing the functionality of software and systems as well as describes the approach, objectives, resources, schedule, and scope of a software testing effort. It identifies the items to be and not to be tested, who will do the testing, the test approach to follow, the pass/fail criteria, training needs for team, etc. Use a test plan to eliminate bugs and other errors in your software before it becomes available online and/or to customers. 
Follow these steps to create a system test plan.