The big thing to test is hovercraft, amphibious units, and sea units with how they travel around structures on top and below the surface of the water.

Also worth checking placing structures and pathing around the edges of the map.

Updates since 2113:

Fixed: Units found a way to get stuck on the corner of buildings if the buildings were placed in specific spots and the unit approached from a specific angle and the path ran along the building's edge.
Fixed: Amphibious units had trouble navigating around underwater buildings.

You can test the latest release candidate by selecting “Engine Test”, under Config, on the Launcher, click Update, then click Start.