re-adds and re-implements the heretic unit test (#93762)

## About The Pull Request
holy shit this was agony to do.
re-implements the heretic unit test in a way that works with the new
system of multiple list while being as thorough as possible

## Why It's Good For The Game
seeing unused knowledges good, which this has already found

## Changelog

🆑
code: heretic unit test is back
/🆑

code/modules/antagonists/heretic/knowledge/heretic_armor_knowledge.dm

@@ -9,6 +9,7 @@
 		list(/obj/structure/table, /obj/item/clothing/suit) = 1,
 		/obj/item/clothing/mask = 1,
 	)
+	abstract_parent_type = /datum/heretic_knowledge/armor
 	result_atoms = list(/obj/item/clothing/suit/hooded/cultrobes/eldritch)
 	cost = 1
 

code/modules/antagonists/heretic/knowledge/rust_lore.dm

@@ -111,13 +111,6 @@
 	cost = 2
 	is_final_knowledge = TRUE
 
-/datum/heretic_knowledge/mark/rust_mark
-	name = "Mark of Rust"
-	desc = "Your Mansus Grasp now applies the Mark of Rust. The mark is triggered from an attack with your Rusty Blade. \
-		When triggered, your victim will suffer heavy disgust and confusion. \
-		Allows you to rust reinforced walls and floors as well as plasteel."
-	gain_text = "The Blacksmith looks away. To a place lost long ago. \"Rusted Hills help those in dire need... at a cost.\""
-
 /datum/heretic_knowledge/spell/rust_construction
 	name = "Rust Construction"
 	desc = "Grants you Rust Construction, a spell that allows you to raise a wall out of a rusted floor. \

code/modules/unit_tests/_unit_tests.dm

@@ -174,6 +174,7 @@
 #include "gloves_and_shoes_armor.dm"
 #include "greyscale_config.dm"
 #include "hallucination_icons.dm"
+#include "heretic_knowledge.dm"
 #include "heretic_rituals.dm"
 #include "high_five.dm"
 #include "holder_loving.dm"

code/modules/unit_tests/heretic_knowledge.dm

@@ -0,0 +1,96 @@
+
+/*
+ * This test checks all heretic knowledge nodes and validates they are setup correctly.
+ * We check that all knowledge is reachable by players (through the research tree)
+ * and that all knowledge have a valid next_knowledge list.
+ */
+/datum/unit_test/heretic_knowledge
+
+/datum/unit_test/heretic_knowledge/Run()
+	GLOB.heretic_path_knowledges = generate_global_heretic_tree()
+
+
+	var/list/start_knowledges = list()
+	generate_heretic_starting_knowledge(start_knowledges)
+	start_knowledges = flatten_list(start_knowledges)
+	var/list/all_knowledges = start_knowledges
+
+	// we need to generate a set of shop_knowledges and drafted knowledges as they're unique per path and slightly random in drafted knowledges
+	for(var/path in GLOB.heretic_path_knowledges)
+		var/list/tree = GLOB.heretic_path_knowledges[path]
+		var/list/shop = list()
+		var/list/draft = list()
+		determine_drafted_knowledge(path, tree, shop, draft)
+		all_knowledges += flatten_list(tree)
+		all_knowledges += flatten_list(shop)
+		all_knowledges += flatten_list(draft)
+
+
+	var/list/all_possible_knowledge = typesof(/datum/heretic_knowledge)
+
+	for(var/datum/heretic_knowledge/knowledge_type as anything in all_possible_knowledge)
+		if(initial(knowledge_type.abstract_parent_type) == knowledge_type)
+			all_possible_knowledge -= knowledge_type
+
+	var/list/list_to_check = get_knowledge_unlockables(start_knowledges, all_knowledges)
+
+	// We now have a list that SHOULD contain all knowledges with a path set (list_to_check).
+	// Let's compare it to our original list (all_possible_knowledge). If they're not identical,
+	// then somewhere we missed a knowledge somewhere, and should throw a fail.
+	var/list/unreachables = list()
+	for(var/knowledge_path in all_possible_knowledge)
+		var/found = FALSE
+		for(var/list/knowledge_node as anything in list_to_check)
+			var/type = knowledge_node["type"]
+			if(type == knowledge_path)
+				found = TRUE
+				break
+		if(!found)
+			unreachables += knowledge_path
+	// Unreachables is a list of typepaths - all paths that cannot be obtained.
+	for(var/datum/heretic_knowledge/lost_knowledge as anything in unreachables)
+		TEST_FAIL("Heretic Knowledge: [lost_knowledge] is unreachable by players! Add it to another knowledge's 'next_knowledge' list. If it is purposeful, set its route to 'null'.")
+
+/// Expects a flat list of knowledge nodes. Returns a list of all HKT_ID entries
+/datum/unit_test/heretic_knowledge/proc/get_knowledge_ids(list/knowledges)
+	var/list/ids = list()
+	for(var/list/knowledge_node as anything in knowledges)
+		ids += knowledge_node[HKT_ID]
+	return ids
+
+/// Gets all unique HKT_NEXT entries from a list of knowledges. both lists must be flat lists of knowledge nodes
+/datum/unit_test/heretic_knowledge/proc/get_knowledge_unlockables(list/starting_point, list/all_knowledges)
+	// Now, let's build a list of all researchable knowledge
+	// from the ground up. We start with all starting knowledge,
+	// then add the next possible knowledges back into the list
+	// repeatedly, until we run out of knowledges to add.
+	var/list/list_to_check = starting_point.Copy()
+	var/i = 0
+	while(i < length(list_to_check))
+		var/list/knowledge_node = list_to_check[++i]
+		// Next knowledge is a list of id that consists of typepath_shopcategory
+		// we basically need to go through the entire chain of HKT_NEXT's to validate the paths's starting from GLOB.heretic_start_knowledge
+		for(var/next_id in knowledge_node[HKT_NEXT])
+			var/list/next_knowledge_node = find_knowledge_node_by_id(all_knowledges, next_id)
+			var/datum/knowledge_path = next_knowledge_node["type"]
+			if(isnull(next_knowledge_node))
+				TEST_FAIL("Heretic Knowledge: [next_id] in [knowledge_path] 's next_knowledge list does not point to a valid knowledge node!")
+				continue
+			if(!istext(next_id))
+				TEST_FAIL("Heretic Knowledge: [next_id] has an invalid non-string next_knowledge entry (Got: [next_id])!")
+			list_to_check += list(next_knowledge_node)
+	return list_to_check
+
+/datum/unit_test/heretic_knowledge/proc/find_knowledge_node_by_id(list/knowledges, id)
+	for(var/list/knowledge_node as anything in knowledges)
+		if(knowledge_node[HKT_ID] == id)
+			return knowledge_node
+	return null
+
+/datum/unit_test/heretic_knowledge/proc/flatten_list(list/knowledge_nodes)
+	var/list/flat_list = list()
+	for(var/datum/heretic_knowledge/knowledge_path as anything in knowledge_nodes)
+		var/list/knowledge_node = knowledge_nodes[knowledge_path]
+		knowledge_node["type"] = knowledge_path
+		flat_list += list(knowledge_node)
+	return flat_list