Test which ad format perform well by applying different formats on your mobile app. Begin by developing variants once you've decided on which page and ad format/type to test.
Test different types of ad dimension and find which dimension gets most impressions.
Ad placement test is done for getting insights about which placement gets better CTR.
Testing which ad combination generate better revenue. It is possible to generate variants of whole ad layouts using particular combinations of different ad formats, sizes, and placements using ad layout testing tools.
It is important to know which ad variation gets better impressions/CTR on which device.
Examine which text ad presentation has the highest CTR.