Devtest game: Update biome registrations (#9936)

games/devtest/mods/mapgen/init.lua

@@ -61,8 +61,13 @@ if minetest.settings:get_bool("devtest_register_biomes", true) then
 		depth_top = 1,
 		node_filler = "basenodes:dirt",
 		depth_filler = 1,
-		y_min = 5,
+		node_riverbed = "basenodes:sand",
+		depth_riverbed = 2,
+		node_dungeon = "basenodes:cobble",
+		node_dungeon_alt = "basenodes:mossycobble",
+		node_dungeon_stair = "stairs:stair_cobble",
 		y_max = 31000,
+		y_min = 4,
 		heat_point = 50,
 		humidity_point = 50,
 	})
@@ -72,9 +77,27 @@ if minetest.settings:get_bool("devtest_register_biomes", true) then
 		node_top = "basenodes:sand",
 		depth_top = 1,
 		node_filler = "basenodes:sand",
-		depth_filler = 2,
+		depth_filler = 3,
+		node_riverbed = "basenodes:sand",
+		depth_riverbed = 2,
+		node_cave_liquid = "basenodes:water_source",
+		node_dungeon = "basenodes:cobble",
+		node_dungeon_alt = "basenodes:mossycobble",
+		node_dungeon_stair = "stairs:stair_cobble",
+		y_max = 3,
+		y_min = -255,
+		heat_point = 50,
+		humidity_point = 50,
+	})
+
+	minetest.register_biome({
+		name = "mapgen:grassland_under",
+		node_cave_liquid = {"basenodes:water_source", "basenodes:lava_source"},
+		node_dungeon = "basenodes:cobble",
+		node_dungeon_alt = "basenodes:mossycobble",
+		node_dungeon_stair = "stairs:stair_cobble",
+		y_max = -256,
 		y_min = -31000,
-		y_max = 4,
 		heat_point = 50,
 		humidity_point = 50,
 	})