It should take up to one hour to finish the application; however, there is an option for you to save it and go back to it at a later stage. . The Aon grid challenge test is a fast-paced attention and memory assessment used in pre-employment evaluations. The first day will be relaxed and will not feature many exercises. Remember. . Practice with some simple slow breathing to get your heart rate down and your cortisol under control. If you find your mind drifting back to "what if I mess up" type thinking, consciously refocus on the task right in front of you. There are questions in between these grids. . The National Grid tests are typically provided by CEB SHL.