byond - Modules - Types

code/game/objects/effects/landmarks/landmarks.dm

/obj/effect/landmark/unit_test_bottom_leftMarks the bottom left of the testing zone. In landmarks.dm and not unit_test.dm so it is always active in the mapping tools.
/obj/effect/landmark/unit_test_top_rightMarks the top right of the testing zone. In landmarks.dm and not unit_test.dm so it is always active in the mapping tools.