Map zones follow load order and mod reloads; mod unit tests

tests/MapZoneServiceTests.cs

@@ -0,0 +1,36 @@
+namespace Cthangover.Mods.Map.Tests
+{
+    using System.Collections.Generic;
+    using Cthangover.Core.Mods.Testing;
+
+    /// <summary>
+    /// Zone lists arrive in mod load order, and a mod that ships a zone with an
+    /// id already defined replaces it — the same rule as every other mod
+    /// resource, so a dependent mod can reshape a zone of the mod it builds on.
+    /// </summary>
+    public class MapZoneServiceTests
+    {
+        [ModTest("zones/later_definition_replaces_earlier")]
+        static void LaterDefinitionReplacesEarlier(ModTestContext ctx)
+        {
+            var service = MapZoneService.Instance;
+            try
+            {
+                service.LoadZones(new List<MapZone>
+                {
+                    new() { ID = "test_zone", Title = "owner" },
+                    new() { ID = "test_other", Title = "other" },
+                    new() { ID = "TEST_ZONE", Title = "dependent" },
+                });
+
+                ModAssert.Equal(2, service.Zones.Count, "zone count");
+                ModAssert.Equal("dependent", service.Get("test_zone").Title, "the later definition wins");
+                ModAssert.Equal("dependent", service.Zones[0].Title, "it keeps the replaced zone's place");
+            }
+            finally
+            {
+                service.ReloadFromMods();
+            }
+        }
+    }
+}