Unit Test For Invalid Map Templates

code/modules/unit_tests/_unit_tests.dm

@@ -3,6 +3,7 @@
 
 #ifdef UNIT_TESTS
 #include "component_tests.dm"
+#include "map_templates.dm"
 #include "reagent_id_typos.dm"
 #include "spawn_humans.dm"
 #include "sql.dm"

code/modules/unit_tests/map_templates.dm

@@ -0,0 +1,7 @@
+/datum/unit_test/map_templates/Run()
+	var/list/datum/map_template/templates = subtypesof(/datum/map_template)
+	for(var/I in templates)
+		var/datum/map_template/MT = new I // The new is important here to ensure stuff gets set properly
+		// Check if it even has a path and if so, does it exist
+		if(MT.mappath && !fexists(MT.mappath))
+			Fail("The map file for [MT.type] does not exist!")