Adds a unit test for species changes keeping clothings (#69788)

* Adds a unit test for species changes keeping clothings

Adds a unit test that checks if people who species change into a Lizard keeps their non-digitigrade shoes or not, which will also affect Monkeys.

code/modules/unit_tests/_unit_tests.dm

@@ -151,6 +151,7 @@
 #include "slips.dm"
 #include "spawn_humans.dm"
 #include "spawn_mobs.dm"
+#include "species_change_clothing.dm"
 #include "species_config_sanity.dm"
 #include "species_unique_id.dm"
 #include "species_whitelists.dm"

code/modules/unit_tests/species_change_clothing.dm

@@ -0,0 +1,16 @@
+///Gives a Human lizard-incompatible shoes, then changes their species over to see if they drop the now incompatible shoes.
+/datum/unit_test/species_change_clothing
+
+/datum/unit_test/species_change_clothing/Run()
+	// Test lizards as their own thing so we can get more coverage on their features
+	var/mob/living/carbon/human/human_to_lizard = allocate(/mob/living/carbon/human/dummy/consistent)
+	human_to_lizard.equipOutfit(/datum/outfit/job/assistant/consistent)
+	human_to_lizard.dna.features["legs"] = DIGITIGRADE_LEGS //you WILL have digitigrade legs
+
+	var/obj/item/human_shoes = human_to_lizard.get_item_by_slot(ITEM_SLOT_FEET)
+	human_shoes.supports_variations_flags = NONE //do not fit lizards at all costs.
+
+	human_to_lizard.set_species(/datum/species/lizard)
+
+	var/obj/item/lizard_shoes = human_to_lizard.get_item_by_slot(ITEM_SLOT_FEET)
+	TEST_ASSERT_NOTEQUAL(human_shoes, lizard_shoes, "Lizard still has shoes after changing species.")