Refactor stress test files for improved readability and functionality

- Simplified the reify stress test by consolidating the reifyInstance call into a single line for better clarity.
- Added a cleanup function in the stressPatterns test to manage knownIds, ensuring that IDs of destroyed instances are removed.
- Enhanced the logic for adding, removing, and updating instances in the stressPatterns test to verify the existence of parent and child instances before operations, improving test robustness.
- Reformatted code in LargeTreeGenerator and MockApiContext for consistency and readability.

plugin/src/Reconciler/reify.stress.spec.lua

@@ -527,13 +527,8 @@ return function()
 
 			local startTime = os.clock()
 			local deferredRefs = {}
-			local unappliedPatch = reifyInstance(
-				deferredRefs,
-				instanceMap,
-				treeData.virtualInstances,
-				treeData.rootId,
-				container
-			)
+			local unappliedPatch =
+				reifyInstance(deferredRefs, instanceMap, treeData.virtualInstances, treeData.rootId, container)
 			applyDeferredRefs(instanceMap, deferredRefs, unappliedPatch)
 			local elapsed = os.clock() - startTime
 

plugin/src/chaos/stressPatterns.spec.lua

@@ -266,12 +266,26 @@ return function()
 
 			local knownIds = { rootId }
 
+			-- Helper to clean up knownIds by removing IDs that no longer exist in instanceMap.
+			-- This is necessary because when a parent is removed, its children are also
+			-- destroyed by Roblox, but their IDs may still be in knownIds.
+			local function cleanupKnownIds()
+				local validIds = {}
+				for _, id in ipairs(knownIds) do
+					if instanceMap.fromIds[id] ~= nil then
+						table.insert(validIds, id)
+					end
+				end
+				knownIds = validIds
+			end
+
 			for _ = 1, 100 do
 				local operation = math.random(1, 3)
 
 				if operation == 1 and #knownIds < 500 then
-					-- Add
+					-- Add: verify parent still exists (may have been destroyed as descendant)
 					local parentId = knownIds[math.random(1, #knownIds)]
+					if instanceMap.fromIds[parentId] ~= nil then
 						local patch = PatchGenerator.createAdditionsPatch({
 							count = 1,
 							parentId = parentId,
@@ -280,6 +294,7 @@ return function()
 						for id in pairs(patch.added) do
 							table.insert(knownIds, id)
 						end
+					end
 				elseif operation == 2 and #knownIds > 1 then
 					-- Remove (not root)
 					local indexToRemove = math.random(2, #knownIds)
@@ -288,9 +303,13 @@ return function()
 
 					local patch = PatchGenerator.createRemovalsPatch({ ids = { idToRemove } })
 					applyPatch(instanceMap, patch)
+
+					-- Clean up knownIds to remove any descendants that were destroyed
+					cleanupKnownIds()
 				elseif operation == 3 and #knownIds > 0 then
-					-- Update
+					-- Update: verify instance still exists
 					local idToUpdate = knownIds[math.random(1, #knownIds)]
+					if instanceMap.fromIds[idToUpdate] ~= nil then
 						local patch = PatchSet.newEmpty()
 						table.insert(patch.updated, {
 							id = idToUpdate,
@@ -300,6 +319,7 @@ return function()
 						applyPatch(instanceMap, patch)
 					end
 				end
+			end
 
 			instanceMap:stop()
 		end)

plugin/src/testUtils/LargeTreeGenerator.lua

@@ -208,7 +208,8 @@ function LargeTreeGenerator.createVirtualTree(options)
 			if withDuplicates and currentDepth <= 1 then
 				for _ = 1, duplicateCount do
 					local duplicateName = prefix .. "_1" -- Same as first child
-					local duplicateId = createVirtualInstance(duplicateName, id, currentDepth + 1, duplicateName .. "_dup")
+					local duplicateId =
+						createVirtualInstance(duplicateName, id, currentDepth + 1, duplicateName .. "_dup")
 					table.insert(children, duplicateId)
 				end
 			end

plugin/src/testUtils/MockApiContext.lua

@@ -108,7 +108,8 @@ function MockApiContext:connect()
 	end
 
 	-- Default connect response
-	return true, {
+	return true,
+		{
 			serverVersion = "0.0.0-mock",
 			protocolVersion = 4,
 			sessionId = HttpService:GenerateGUID(false),