Inventory refuses non-positive counts; unknown saved items kept; factories follow reloads

tests/ItemsSaveableTests.cs

@@ -0,0 +1,54 @@
+namespace Cthangover.Mods.Items.Tests
+{
+    using System.Collections.Generic;
+    using System.Linq;
+    using Cthangover.Core.Items;
+    using Cthangover.Core.Mods.Resolvers;
+    using Cthangover.Core.Mods.Testing;
+    using Cthangover.Core.Settings;
+
+    /// <summary>
+    /// The items slot across a change of the game's content: a save may name
+    /// an item no loaded mod defines any more (its mod was removed or the id
+    /// renamed). Loading it must keep the rest of the inventory usable, and
+    /// the next save must still be written — with the unknown stack kept, so
+    /// it comes back with its mod.
+    /// </summary>
+    public class ItemsSaveableTests
+    {
+        private const string UnknownId = "__test/no_such_item";
+
+        [ModTest("save/unknown_item_survives_load_and_save")]
+        static void UnknownItemSurvivesLoadAndSave(ModTestContext ctx)
+        {
+            var known = Entities.Collect<ItemInfo>().Keys.First();
+            var runtime = GameData.Instance.Runtime;
+            var original = runtime.Inventory;
+            try
+            {
+                runtime.Inventory = new Inventory();
+                var slot = new ModSlot();
+                slot.Data["Inventory"] = new DataBlob(1, new List<CItem>
+                {
+                    new() { ID = known, Count = 4 },
+                    new() { ID = UnknownId, Count = 3 },
+                });
+                var saveable = new ItemsSaveable();
+
+                ModAssert.True(saveable.OnLoad(slot, out _), "slot with an unknown item loads");
+                ModAssert.Equal(4, runtime.Inventory.CheckCount(known), "known stack restored");
+                ModAssert.False(runtime.Inventory.HasItem(UnknownId), "unknown item is not a usable stack");
+
+                var saved = new ModSlot();
+                saveable.OnSave(saved);
+                var items = saved.Data["Inventory"].ReadJson<List<CItem>>();
+                ModAssert.Equal(4, items.Single(i => i.ID == known).Count, "known stack saved");
+                ModAssert.Equal(3, items.Single(i => i.ID == UnknownId).Count, "unknown stack kept in the save");
+            }
+            finally
+            {
+                runtime.Inventory = original;
+            }
+        }
+    }
+}