From 9650cf5eef2499a755f97e5408ef2e253da69a58 Mon Sep 17 00:00:00 2001
From: Iajret Creature
 <122297233+AnArgonianLizardThatStealsPRs@users.noreply.github.com>
Date: Fri, 27 Oct 2023 10:25:02 +0300
Subject: [PATCH] [MIRROR] Shapechange health transfer tweaks [MDB IGNORE]
 (#24590) (#298)

* Shapechange health transfer tweaks

* Fix diffs

---------

Co-authored-by: SkyratBot <59378654+SkyratBot@users.noreply.github.com>
Co-authored-by: Jacquerel <hnevard@gmail.com>
Co-authored-by: Giz <13398309+vinylspiders@users.noreply.github.com>
---
 code/datums/actions/action.dm                 | 59 +++++++++---------
 code/datums/components/leash.dm               |  8 +++
 code/datums/elements/weather_listener.dm      |  2 +-
 .../heretic/magic/ascended_shapeshift.dm      |  1 +
 .../heretic/magic/flesh_ascension.dm          |  1 +
 .../mob/living/carbon/human/_species.dm       | 16 ++---
 code/modules/mob/living/damage_procs.dm       |  4 ++
 .../living/simple_animal/guardian/guardian.dm | 19 +++---
 .../simple_animal/hostile/megafauna/drake.dm  |  2 +-
 code/modules/mob/mob_helpers.dm               |  1 -
 .../spell_types/shapeshift/_shape_status.dm   | 27 +++++----
 code/modules/surgery/bodyparts/_bodyparts.dm  |  2 +-
 code/modules/unit_tests/spell_shapeshift.dm   | 60 ++++++++++++++++---
 13 files changed, 135 insertions(+), 67 deletions(-)

diff --git a/code/datums/actions/action.dm b/code/datums/actions/action.dm
index d81c72cc920..69f8fd42dcf 100644
--- a/code/datums/actions/action.dm
+++ b/code/datums/actions/action.dm
@@ -79,16 +79,17 @@
 
 /// Grants the action to the passed mob, making it the owner
 /datum/action/proc/Grant(mob/grant_to)
-	if(!grant_to)
+	if(isnull(grant_to))
 		Remove(owner)
 		return
-	if(owner)
-		if(owner == grant_to)
-			return
-		Remove(owner)
-	SEND_SIGNAL(src, COMSIG_ACTION_GRANTED, grant_to)
-	SEND_SIGNAL(grant_to, COMSIG_MOB_GRANTED_ACTION, src)
+	if(grant_to == owner)
+		return // We already have it
+	var/mob/previous_owner = owner
 	owner = grant_to
+	if(!isnull(previous_owner))
+		Remove(previous_owner)
+	SEND_SIGNAL(src, COMSIG_ACTION_GRANTED, owner)
+	SEND_SIGNAL(owner, COMSIG_MOB_GRANTED_ACTION, src)
 	RegisterSignal(owner, COMSIG_QDELETING, PROC_REF(clear_ref), override = TRUE)
 
 	// Register some signals based on our check_flags
@@ -120,27 +121,29 @@
 	LAZYREMOVE(remove_from?.actions, src) // We aren't always properly inserted into the viewers list, gotta make sure that action's cleared
 	viewers = list()
 
-	if(owner)
-		SEND_SIGNAL(src, COMSIG_ACTION_REMOVED, owner)
-		SEND_SIGNAL(owner, COMSIG_MOB_REMOVED_ACTION, src)
-		UnregisterSignal(owner, COMSIG_QDELETING)
-
-		// Clean up our check_flag signals
-		UnregisterSignal(owner, list(
-			COMSIG_LIVING_SET_BODY_POSITION,
-			COMSIG_MOB_STATCHANGE,
-			SIGNAL_ADDTRAIT(TRAIT_HANDS_BLOCKED),
-			SIGNAL_ADDTRAIT(TRAIT_IMMOBILIZED),
-			SIGNAL_ADDTRAIT(TRAIT_INCAPACITATED),
-			SIGNAL_ADDTRAIT(TRAIT_MAGICALLY_PHASED),
-			SIGNAL_REMOVETRAIT(TRAIT_HANDS_BLOCKED),
-			SIGNAL_REMOVETRAIT(TRAIT_IMMOBILIZED),
-			SIGNAL_REMOVETRAIT(TRAIT_INCAPACITATED),
-			SIGNAL_REMOVETRAIT(TRAIT_MAGICALLY_PHASED),
-		))
-
-		if(target == owner)
-			RegisterSignal(target, COMSIG_QDELETING, PROC_REF(clear_ref))
+	if(isnull(owner))
+		return
+	SEND_SIGNAL(src, COMSIG_ACTION_REMOVED, owner)
+	SEND_SIGNAL(owner, COMSIG_MOB_REMOVED_ACTION, src)
+	UnregisterSignal(owner, COMSIG_QDELETING)
+
+	// Clean up our check_flag signals
+	UnregisterSignal(owner, list(
+		COMSIG_LIVING_SET_BODY_POSITION,
+		COMSIG_MOB_STATCHANGE,
+		SIGNAL_ADDTRAIT(TRAIT_HANDS_BLOCKED),
+		SIGNAL_ADDTRAIT(TRAIT_IMMOBILIZED),
+		SIGNAL_ADDTRAIT(TRAIT_INCAPACITATED),
+		SIGNAL_ADDTRAIT(TRAIT_MAGICALLY_PHASED),
+		SIGNAL_REMOVETRAIT(TRAIT_HANDS_BLOCKED),
+		SIGNAL_REMOVETRAIT(TRAIT_IMMOBILIZED),
+		SIGNAL_REMOVETRAIT(TRAIT_INCAPACITATED),
+		SIGNAL_REMOVETRAIT(TRAIT_MAGICALLY_PHASED),
+	))
+
+	if(target == owner)
+		RegisterSignal(target, COMSIG_QDELETING, PROC_REF(clear_ref))
+	if (owner == remove_from)
 		owner = null
 
 /// Actually triggers the effects of the action.
diff --git a/code/datums/components/leash.dm b/code/datums/components/leash.dm
index d04a482dbf6..ef0b278c799 100644
--- a/code/datums/components/leash.dm
+++ b/code/datums/components/leash.dm
@@ -109,6 +109,14 @@
 	if (get_dist(parent, owner) <= distance)
 		return
 
+	var/atom/movable/atom_parent = parent
+	if (isnull(owner.loc))
+		atom_parent.moveToNullspace() // If our parent is in nullspace I guess we gotta go there too
+		return
+	if (isnull(atom_parent.loc))
+		force_teleport_back("in nullspace") // If we're in nullspace, get outta there
+		return
+
 	SEND_SIGNAL(parent, COMSIG_LEASH_PATH_STARTED)
 
 	current_path_tick += 1
diff --git a/code/datums/elements/weather_listener.dm b/code/datums/elements/weather_listener.dm
index 61778e2a186..0028f57ff3d 100644
--- a/code/datums/elements/weather_listener.dm
+++ b/code/datums/elements/weather_listener.dm
@@ -35,7 +35,7 @@
 /datum/element/weather_listener/proc/handle_z_level_change(datum/source, turf/old_loc, turf/new_loc)
 	SIGNAL_HANDLER
 	var/list/fitting_z_levels = SSmapping.levels_by_trait(weather_trait)
-	if(!(new_loc.z in fitting_z_levels))
+	if(!(new_loc?.z in fitting_z_levels))
 		return
 	var/datum/component/our_comp = source.AddComponent(\
 		/datum/component/area_sound_manager, \
diff --git a/code/modules/antagonists/heretic/magic/ascended_shapeshift.dm b/code/modules/antagonists/heretic/magic/ascended_shapeshift.dm
index f1d6de56e39..e11053fd3e3 100644
--- a/code/modules/antagonists/heretic/magic/ascended_shapeshift.dm
+++ b/code/modules/antagonists/heretic/magic/ascended_shapeshift.dm
@@ -4,6 +4,7 @@
 	desc = "A spell that allows you to take on the form of another eldritch creature, gaining their abilities. \
 		You can change your choice at any time, and if your form dies, you dont die."
 	cooldown_time = 20 SECONDS
+	convert_damage = FALSE
 	die_with_shapeshifted_form = FALSE
 	possible_shapes = list(
 		/mob/living/basic/heretic_summon/ash_spirit,
diff --git a/code/modules/antagonists/heretic/magic/flesh_ascension.dm b/code/modules/antagonists/heretic/magic/flesh_ascension.dm
index d086c1127fc..a2d792080e0 100644
--- a/code/modules/antagonists/heretic/magic/flesh_ascension.dm
+++ b/code/modules/antagonists/heretic/magic/flesh_ascension.dm
@@ -13,6 +13,7 @@
 	invocation_type = INVOCATION_SHOUT
 	spell_requirements = NONE
 
+	convert_damage = FALSE // Functionally meaningless on Armsy, we track how many segments it had instead
 	possible_shapes = list(/mob/living/basic/heretic_summon/armsy)
 
 	/// The length of our new wormy when we shed.
diff --git a/code/modules/mob/living/carbon/human/_species.dm b/code/modules/mob/living/carbon/human/_species.dm
index 2ba24884ded..d92dde594dd 100644
--- a/code/modules/mob/living/carbon/human/_species.dm
+++ b/code/modules/mob/living/carbon/human/_species.dm
@@ -1422,32 +1422,32 @@ GLOBAL_LIST_EMPTY(features_by_species)
 			H.damageoverlaytemp = 20
 			var/damage_amount = forced ? damage : damage * hit_percent * H.physiology.brute_mod
 			if(BP)
-				if(BP.receive_damage(damage_amount, 0, wound_bonus = wound_bonus, bare_wound_bonus = bare_wound_bonus, sharpness = sharpness, attack_direction = attack_direction, damage_source = attacking_item))
+				if(BP.receive_damage(damage_amount, 0, forced = forced, wound_bonus = wound_bonus, bare_wound_bonus = bare_wound_bonus, sharpness = sharpness, attack_direction = attack_direction, damage_source = attacking_item))
 					H.update_damage_overlays()
 			else//no bodypart, we deal damage with a more general method.
-				H.adjustBruteLoss(damage_amount)
+				H.adjustBruteLoss(damage_amount, forced = forced)
 			INVOKE_ASYNC(H, TYPE_PROC_REF(/mob/living/carbon/human, adjust_pain), damage_amount) // SKYRAT EDIT ADDITION - ERP Pain
 		if(BURN)
 			H.damageoverlaytemp = 20
 			var/damage_amount = forced ? damage : damage * hit_percent * H.physiology.burn_mod
 			if(BP)
-				if(BP.receive_damage(0, damage_amount, wound_bonus = wound_bonus, bare_wound_bonus = bare_wound_bonus, sharpness = sharpness, attack_direction = attack_direction, damage_source = attacking_item))
+				if(BP.receive_damage(0, damage_amount, forced = forced, wound_bonus = wound_bonus, bare_wound_bonus = bare_wound_bonus, sharpness = sharpness, attack_direction = attack_direction, damage_source = attacking_item))
 					H.update_damage_overlays()
 			else
-				H.adjustFireLoss(damage_amount)
+				H.adjustFireLoss(damage_amount, forced = forced)
 			INVOKE_ASYNC(H, TYPE_PROC_REF(/mob/living/carbon/human, adjust_pain), damage_amount) // SKYRAT EDIT ADDITION - ERP Pain
 		if(TOX)
 			var/damage_amount = forced ? damage : damage * hit_percent * H.physiology.tox_mod
-			H.adjustToxLoss(damage_amount)
+			H.adjustToxLoss(damage_amount, forced = forced)
 		if(OXY)
 			var/damage_amount = forced ? damage : damage * hit_percent * H.physiology.oxy_mod
-			H.adjustOxyLoss(damage_amount)
+			H.adjustOxyLoss(damage_amount, forced = forced)
 		if(CLONE)
 			var/damage_amount = forced ? damage : damage * hit_percent * H.physiology.clone_mod
-			H.adjustCloneLoss(damage_amount)
+			H.adjustCloneLoss(damage_amount, forced = forced)
 		if(STAMINA)
 			var/damage_amount = forced ? damage : damage * hit_percent * H.physiology.stamina_mod
-			H.adjustStaminaLoss(damage_amount)
+			H.adjustStaminaLoss(damage_amount, forced = forced)
 		if(BRAIN)
 			var/damage_amount = forced ? damage : damage * hit_percent * H.physiology.brain_mod
 			H.adjustOrganLoss(ORGAN_SLOT_BRAIN, damage_amount)
diff --git a/code/modules/mob/living/damage_procs.dm b/code/modules/mob/living/damage_procs.dm
index a58d92ab7e9..c92262733c1 100644
--- a/code/modules/mob/living/damage_procs.dm
+++ b/code/modules/mob/living/damage_procs.dm
@@ -68,6 +68,10 @@
 		if(STAMINA)
 			return getStaminaLoss()
 
+/// return the total damage of all types which update your health
+/mob/living/proc/get_total_damage(precision = DAMAGE_PRECISION)
+	return round(getBruteLoss() + getFireLoss() + getToxLoss() + getOxyLoss() + getCloneLoss(), precision)
+
 /// applies multiple damages at once via [/mob/living/proc/apply_damage]
 /mob/living/proc/apply_damages(brute = 0, burn = 0, tox = 0, oxy = 0, clone = 0, def_zone = null, blocked = FALSE, stamina = 0, brain = 0)
 	if(blocked >= 100)
diff --git a/code/modules/mob/living/simple_animal/guardian/guardian.dm b/code/modules/mob/living/simple_animal/guardian/guardian.dm
index 4ca35a67357..21286787755 100644
--- a/code/modules/mob/living/simple_animal/guardian/guardian.dm
+++ b/code/modules/mob/living/simple_animal/guardian/guardian.dm
@@ -138,7 +138,9 @@ GLOBAL_LIST_EMPTY(parasites) //all currently existing/living guardians
 /mob/living/simple_animal/hostile/guardian/proc/cut_summoner(different_person = FALSE)
 	if(is_deployed())
 		recall_effects()
-	forceMove(get_turf(src))
+	var/summoner_turf = get_turf(src)
+	if (!isnull(summoner_turf))
+		forceMove(summoner_turf)
 	UnregisterSignal(summoner, list(COMSIG_MOVABLE_MOVED, COMSIG_QDELETING, COMSIG_LIVING_DEATH, COMSIG_LIVING_HEALTH_UPDATE, COMSIG_LIVING_ON_WABBAJACKED, COMSIG_LIVING_SHAPESHIFTED, COMSIG_LIVING_UNSHAPESHIFTED))
 	if(different_person)
 		summoner.faction -= "[REF(src)]"
@@ -311,7 +313,8 @@ GLOBAL_LIST_EMPTY(parasites) //all currently existing/living guardians
 	SIGNAL_HANDLER
 
 	cut_summoner()
-	forceMove(source.loc)
+	if (!isnull(source.loc))
+		forceMove(source.loc)
 	to_chat(src, span_danger("Your summoner has died!"))
 	visible_message(span_bolddanger("\The [src] dies along with its user!"))
 	source.visible_message(span_bolddanger("[source]'s body is completely consumed by the strain of sustaining [src]!"))
@@ -346,12 +349,12 @@ GLOBAL_LIST_EMPTY(parasites) //all currently existing/living guardians
 		return
 	to_chat(src, span_holoparasite("You moved out of range, and were pulled back! You can only move [range] meters from [summoner.real_name]!"))
 	visible_message(span_danger("\The [src] jumps back to its user."))
-	if(istype(summoner.loc, /obj/effect))
+	new /obj/effect/temp_visual/guardian/phase/out(loc)
+	if(istype(summoner.loc, /obj/effect) || isnull(summoner.loc))
 		recall(forced = TRUE)
-	else
-		new /obj/effect/temp_visual/guardian/phase/out(loc)
-		forceMove(summoner.loc)
-		new /obj/effect/temp_visual/guardian/phase(loc)
+		return
+	forceMove(summoner.loc)
+	new /obj/effect/temp_visual/guardian/phase(loc)
 
 /mob/living/simple_animal/hostile/guardian/can_suicide()
 	return FALSE
@@ -469,7 +472,7 @@ GLOBAL_LIST_EMPTY(parasites) //all currently existing/living guardians
 //MANIFEST, RECALL, TOGGLE MODE/LIGHT, SHOW TYPE
 
 /mob/living/simple_animal/hostile/guardian/proc/manifest(forced)
-	if(is_deployed() || istype(summoner.loc, /obj/effect) || (!COOLDOWN_FINISHED(src, manifest_cooldown) && !forced) || locked)
+	if(is_deployed() || isnull(summoner.loc) || istype(summoner.loc, /obj/effect) || (!COOLDOWN_FINISHED(src, manifest_cooldown) && !forced) || locked)
 		return FALSE
 	forceMove(summoner.loc)
 	new /obj/effect/temp_visual/guardian/phase(loc)
diff --git a/code/modules/mob/living/simple_animal/hostile/megafauna/drake.dm b/code/modules/mob/living/simple_animal/hostile/megafauna/drake.dm
index 1aadefd4153..5008d4b1748 100644
--- a/code/modules/mob/living/simple_animal/hostile/megafauna/drake.dm
+++ b/code/modules/mob/living/simple_animal/hostile/megafauna/drake.dm
@@ -322,7 +322,7 @@
 
 /mob/living/simple_animal/hostile/megafauna/dragon/lesser/adjustHealth(amount, updating_health = TRUE, forced = FALSE)
 	. = ..()
-	lava_swoop.enraged = FALSE
+	lava_swoop?.enraged = FALSE // In case taking damage caused us to start deleting ourselves
 
 /mob/living/simple_animal/hostile/megafauna/dragon/lesser/grant_achievement(medaltype,scoretype)
 	return
diff --git a/code/modules/mob/mob_helpers.dm b/code/modules/mob/mob_helpers.dm
index cb041a6ab35..5f52e79aaab 100644
--- a/code/modules/mob/mob_helpers.dm
+++ b/code/modules/mob/mob_helpers.dm
@@ -84,7 +84,6 @@
 			CRASH("limbs is empty and the chest is blacklisted. this may not be intended!")
 	return (((chest_blacklisted && !base_zone) || even_weights) ? pick_weight(limbs) : ran_zone(base_zone, base_probability, limbs))
 
-
 ///Would this zone be above the neck
 /proc/above_neck(zone)
 	var/list/zones = list(BODY_ZONE_HEAD, BODY_ZONE_PRECISE_MOUTH, BODY_ZONE_PRECISE_EYES)
diff --git a/code/modules/spells/spell_types/shapeshift/_shape_status.dm b/code/modules/spells/spell_types/shapeshift/_shape_status.dm
index 94e1d549af2..ba8269108a8 100644
--- a/code/modules/spells/spell_types/shapeshift/_shape_status.dm
+++ b/code/modules/spells/spell_types/shapeshift/_shape_status.dm
@@ -76,20 +76,27 @@
 	UnregisterSignal(owner, list(COMSIG_LIVING_PRE_WABBAJACKED, COMSIG_LIVING_DEATH))
 	UnregisterSignal(caster_mob, list(COMSIG_QDELETING, COMSIG_LIVING_DEATH))
 
-	caster_mob.forceMove(owner.loc)
 	REMOVE_TRAIT(caster_mob, TRAIT_NO_TRANSFORM, REF(src))
 	caster_mob.remove_status_effect(/datum/status_effect/grouped/stasis, STASIS_SHAPECHANGE_EFFECT)
-	owner.mind?.transfer_to(caster_mob)
+
+	var/atom/former_loc = owner.loc
+	owner.moveToNullspace()
+	caster_mob.forceMove(former_loc) // This is to avoid crushing our former cockroach body
 
 	if(kill_caster_after)
 		caster_mob.death()
 
 	after_unchange()
-	caster_mob = null
+
+	// We're about to remove the status effect and clear owner so we need to cache this
+	var/mob/living/former_body = owner
+
+	// Do this late as it will destroy the status effect we are in and null a bunch of values we are trying to use
+	owner.mind?.transfer_to(caster_mob)
 
 	// Destroy the owner after all's said and done, this will also destroy our status effect (src)
 	// retore_caster() should never reach this point while either the owner or the effect is being qdeleted
-	qdel(owner)
+	qdel(former_body)
 
 /// Effects done after the casting mob has reverted to their human form.
 /datum/status_effect/shapechange_mob/proc/after_unchange()
@@ -154,9 +161,9 @@
 		source_spell.Grant(owner)
 
 		if(source_spell.convert_damage)
-			var/damage_to_apply = owner.maxHealth * ((caster_mob.maxHealth - caster_mob.health) / caster_mob.maxHealth)
+			var/damage_to_apply = owner.maxHealth * (caster_mob.get_total_damage() / caster_mob.maxHealth)
 
-			owner.apply_damage(damage_to_apply, source_spell.convert_damage_type, forced = TRUE, wound_bonus = CANT_WOUND)
+			owner.apply_damage(damage_to_apply, source_spell.convert_damage_type, forced = TRUE, spread_damage = TRUE, wound_bonus = CANT_WOUND)
 			owner.blood_volume = caster_mob.blood_volume
 
 	for(var/datum/action/bodybound_action as anything in caster_mob.actions)
@@ -186,11 +193,9 @@
 	if(QDELETED(source_spell) || !source_spell.convert_damage)
 		return
 
-	if(caster_mob.stat != DEAD)
-		caster_mob.revive(HEAL_DAMAGE)
-
-		var/damage_to_apply = caster_mob.maxHealth * ((owner.maxHealth - owner.health) / owner.maxHealth)
-		caster_mob.apply_damage(damage_to_apply, source_spell.convert_damage_type, forced = TRUE, wound_bonus = CANT_WOUND)
+	caster_mob.fully_heal(HEAL_DAMAGE) // Remove all of our damage before setting our health to a proportion of the former transformed mob's health
+	var/damage_to_apply = caster_mob.maxHealth * (owner.get_total_damage() / owner.maxHealth)
+	caster_mob.apply_damage(damage_to_apply, source_spell.convert_damage_type, forced = TRUE, spread_damage = TRUE, wound_bonus = CANT_WOUND)
 
 	caster_mob.blood_volume = owner.blood_volume
 
diff --git a/code/modules/surgery/bodyparts/_bodyparts.dm b/code/modules/surgery/bodyparts/_bodyparts.dm
index 407ac67a43a..a8f35aaa968 100644
--- a/code/modules/surgery/bodyparts/_bodyparts.dm
+++ b/code/modules/surgery/bodyparts/_bodyparts.dm
@@ -457,7 +457,7 @@
 /obj/item/bodypart/proc/receive_damage(brute = 0, burn = 0, blocked = 0, updating_health = TRUE, forced = FALSE, required_bodytype = null, wound_bonus = 0, bare_wound_bonus = 0, sharpness = NONE, attack_direction = null, damage_source)
 	SHOULD_CALL_PARENT(TRUE)
 
-	var/hit_percent = (100-blocked)/100
+	var/hit_percent = forced ? 1 : (100-blocked)/100
 	if((!brute && !burn) || hit_percent <= 0)
 		return FALSE
 	if (!forced)
diff --git a/code/modules/unit_tests/spell_shapeshift.dm b/code/modules/unit_tests/spell_shapeshift.dm
index 4e2ce659003..9b5804e3520 100644
--- a/code/modules/unit_tests/spell_shapeshift.dm
+++ b/code/modules/unit_tests/spell_shapeshift.dm
@@ -18,6 +18,8 @@
 
 		qdel(shift)
 
+#define TRIGGER_RESET_COOLDOWN(spell) spell.next_use_time = 0; spell.Trigger();
+
 /**
  * Validates that shapeshift spells put the mob in another mob, as they should.
  */
@@ -25,7 +27,7 @@
 
 /datum/unit_test/shapeshift_spell/Run()
 
-	var/mob/living/carbon/human/dummy = allocate(/mob/living/carbon/human/consistent)
+	var/mob/living/carbon/human/dummy = allocate(/mob/living/carbon/human/consistent, run_loc_floor_bottom_left)
 	dummy.mind_initialize()
 
 	for(var/spell_type in subtypesof(/datum/action/cooldown/spell/shapeshift))
@@ -57,8 +59,7 @@
 	if(forced_shape)
 		shift.shapeshift_type = forced_shape
 
-	shift.next_use_time = 0
-	shift.Trigger()
+	TRIGGER_RESET_COOLDOWN(shift)
 	var/mob/expected_shape = shift.shapeshift_type
 	if(!istype(dummy.loc, expected_shape))
 		return TEST_FAIL("Shapeshift spell: [shift.name] failed to transform the dummy into the shape [initial(expected_shape.name)]. \
@@ -68,8 +69,7 @@
 	if(!(shift in shape.actions))
 		return TEST_FAIL("Shapeshift spell: [shift.name] failed to grant the spell to the dummy's shape.")
 
-	shift.next_use_time = 0
-	shift.Trigger()
+	TRIGGER_RESET_COOLDOWN(shift)
 	if(istype(dummy.loc, shift.shapeshift_type))
 		return TEST_FAIL("Shapeshift spell: [shift.name] failed to transform the dummy back into a human.")
 
@@ -81,7 +81,7 @@
 
 /datum/unit_test/shapeshift_holoparasites/Run()
 
-	var/mob/living/carbon/human/dummy = allocate(/mob/living/carbon/human/consistent)
+	var/mob/living/carbon/human/dummy = allocate(/mob/living/carbon/human/consistent, run_loc_floor_bottom_left)
 
 	var/datum/action/cooldown/spell/shapeshift/wizard/shift = new(dummy)
 	shift.shapeshift_type = shift.possible_shapes[1]
@@ -99,9 +99,53 @@
 	TEST_ASSERT_EQUAL(test_stand.summoner, dummy.loc, "Shapeshift spell failed to transfer the holoparasite to the dummy's shape.")
 
 	// Dummy casts shapeshfit back, the stand's summoner should become the dummy again.
-	shift.next_use_time = 0
-	shift.Trigger()
+	TRIGGER_RESET_COOLDOWN(shift)
 	TEST_ASSERT(!istype(dummy.loc, shift.shapeshift_type), "Shapeshift spell failed to transform the dummy back into human form.")
 	TEST_ASSERT_EQUAL(test_stand.summoner, dummy, "Shapeshift spell failed to transfer the holoparasite back to the dummy's human form.")
 
 	qdel(shift)
+
+#define EXPECTED_HEALTH_RATIO 0.5
+
+/// Validates that shapeshifting carries health or death between forms properly, if it is supposed to
+/datum/unit_test/shapeshift_health
+
+/datum/unit_test/shapeshift_health/Run()
+	for(var/spell_type in subtypesof(/datum/action/cooldown/spell/shapeshift))
+		var/mob/living/carbon/human/dummy = allocate(/mob/living/carbon/human/consistent, run_loc_floor_bottom_left)
+		var/datum/action/cooldown/spell/shapeshift/shift_spell = new spell_type(dummy)
+		shift_spell.Grant(dummy)
+		shift_spell.shapeshift_type = shift_spell.possible_shapes[1]
+
+		if (istype(shift_spell, /datum/action/cooldown/spell/shapeshift/polymorph_belt))
+			var/datum/action/cooldown/spell/shapeshift/polymorph_belt/belt_spell = shift_spell
+			belt_spell.channel_time = 0 SECONDS // No do-afters
+
+		if (shift_spell.convert_damage)
+			shift_spell.Trigger()
+			TEST_ASSERT(istype(dummy.loc, shift_spell.shapeshift_type), "Failed to transform into [shift_spell.shapeshift_type]using [shift_spell.name].")
+			var/mob/living/shifted_mob = dummy.loc
+			shifted_mob.apply_damage(shifted_mob.maxHealth * EXPECTED_HEALTH_RATIO, BRUTE, forced = TRUE)
+			TRIGGER_RESET_COOLDOWN(shift_spell)
+			TEST_ASSERT(!istype(dummy.loc, shift_spell.shapeshift_type), "Failed to unfransform from [shift_spell.shapeshift_type] using [shift_spell.name].")
+			TEST_ASSERT_EQUAL(dummy.get_total_damage(), dummy.maxHealth * EXPECTED_HEALTH_RATIO, "Failed to transfer damage from [shift_spell.shapeshift_type] to original form using [shift_spell.name].")
+			TRIGGER_RESET_COOLDOWN(shift_spell)
+			TEST_ASSERT(istype(dummy.loc, shift_spell.shapeshift_type), "Failed to transform into [shift_spell.shapeshift_type] after taking damage using [shift_spell.name].")
+			shifted_mob = dummy.loc
+			TEST_ASSERT_EQUAL(shifted_mob.get_total_damage(), shifted_mob.maxHealth * EXPECTED_HEALTH_RATIO, "Failed to transfer damage from original form to [shift_spell.shapeshift_type] using [shift_spell.name].")
+			TRIGGER_RESET_COOLDOWN(shift_spell)
+
+		if (shift_spell.die_with_shapeshifted_form)
+			TRIGGER_RESET_COOLDOWN(shift_spell)
+			TEST_ASSERT(istype(dummy.loc, shift_spell.shapeshift_type), "Failed to transform into [shift_spell.shapeshift_type]")
+			var/mob/living/shifted_mob = dummy.loc
+			shifted_mob.health = 0 // Fucking megafauna
+			shifted_mob.death()
+			if (shift_spell.revert_on_death)
+				TEST_ASSERT(!istype(dummy.loc, shift_spell.shapeshift_type), "Failed to untransform after death using [shift_spell.name].")
+			TEST_ASSERT_EQUAL(dummy.stat, DEAD, "Failed to kill original mob when transformed mob died using [shift_spell.name].")
+
+		qdel(shift_spell)
+
+#undef EXPECTED_HEALTH_RATIO
+#undef TRIGGER_RESET_COOLDOWN