Add cross-service refs case to serializePlace tests

tests/roblox/files/serializePlace.luau

@@ -2,6 +2,8 @@ local fs = require("@lune/fs")
 local roblox = require("@lune/roblox")
 local Instance = roblox.Instance
 
+-- Smoke tests
+do
 	local game = Instance.new("DataModel")
 
 	local workspace = game:GetService("Workspace")
@@ -29,3 +31,26 @@ assert(savedXml.Name ~= "ROOT")
 
 	assert(savedBinary.ClassName == "DataModel")
 	assert(savedXml.ClassName == "DataModel")
+end
+
+-- Ensure Ref properties are preserved across services
+do
+	local game = Instance.new("DataModel")
+	local ReplicatedStorage = Instance.new("ReplicatedStorage")
+	local Workspace = Instance.new("Workspace")
+
+	Workspace.Parent = game
+	ReplicatedStorage.Parent = game
+
+	local part = Instance.new("Part")
+	part.Parent = ReplicatedStorage
+
+	local objectValue = Instance.new("ObjectValue")
+	objectValue.Value = part
+	objectValue.Parent = Workspace
+
+	local serialized = roblox.serializePlace(game)
+	local deserialized = roblox.deserializePlace(serialized)
+
+	assert(deserialized.Workspace.ObjectValue.Value == deserialized.ReplicatedStorage.Part)
+end