Add test for lookup anchoring (#2035)

* Add test for lookup anchoring

* Updates

* Fix test

Robust.UnitTesting/Shared/EntityLookupTest.cs

@@ -0,0 +1,56 @@
+using System.Linq;
+using System.Threading.Tasks;
+using NUnit.Framework;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Map;
+using Robust.Shared.Maths;
+
+namespace Robust.UnitTesting.Shared
+{
+    [TestFixture, TestOf(typeof(IEntityLookup))]
+    public sealed class EntityLookupTest : RobustIntegrationTest
+    {
+        /// <summary>
+        /// Is the entity correctly removed / added to EntityLookup when anchored
+        /// </summary>
+        [Test]
+        public async Task TestAnchoring()
+        {
+            var server = StartServer();
+            await server.WaitIdleAsync();
+
+            var lookup = server.ResolveDependency<IEntityLookup>();
+            var entManager = server.ResolveDependency<IEntityManager>();
+            var mapManager = server.ResolveDependency<IMapManager>();
+
+            await server.WaitAssertion(() =>
+            {
+                var mapId = mapManager.CreateMap();
+                var grid = mapManager.CreateGrid(mapId);
+
+                var theMapSpotBeingUsed = new Box2(Vector2.Zero, Vector2.One)
+                    ;
+                grid.SetTile(new Vector2i(), new Tile(1));
+
+                lookup.Update();
+                Assert.That(lookup.GetEntitiesIntersecting(mapId, theMapSpotBeingUsed).ToList().Count, Is.EqualTo(1));
+
+                // Setup and check it actually worked
+                var dummy = entManager.SpawnEntity(null, new MapCoordinates(Vector2.Zero, mapId));
+                lookup.Update();
+                Assert.That(lookup.GetEntitiesIntersecting(mapId, theMapSpotBeingUsed).ToList().Count, Is.EqualTo(2));
+
+                // When anchoring should still only be 1 entity.
+                dummy.Transform.Anchored = true;
+                Assert.That(dummy.Transform.Anchored);
+                lookup.Update();
+                Assert.That(lookup.GetEntitiesIntersecting(mapId, theMapSpotBeingUsed).ToList().Count, Is.EqualTo(2));
+
+                // Even when unanchored should still be there
+                dummy.Transform.Anchored = false;
+                lookup.Update();
+                Assert.That(lookup.GetEntitiesIntersecting(mapId, theMapSpotBeingUsed).ToList().Count, Is.EqualTo(2));
+            });
+        }
+    }
+}