Added a character saving unit test.

code/modules/unit_tests/_unit_tests.dm

@@ -3,6 +3,7 @@
 
 #ifdef UNIT_TESTS
 #include "anchored_mobs.dm"
+#include "character_saving.dm"
 #include "component_tests.dm"
 #include "reagent_id_typos.dm"
 #include "reagent_recipe_collisions.dm"

code/modules/unit_tests/character_saving.dm

@@ -0,0 +1,8 @@
+/datum/unit_test/character_saving/Run()
+	try
+		var/datum/preferences/P = new
+		P.load_path("test")
+		P.load_character(0)
+		P.save_character()
+	catch(exception/e)
+		Fail("Failed to save and load character due to exception [e.name]")