test undeclared some

test/EngineTest.cs

@@ -274,5 +274,25 @@ namespace Tests
 
             Assert.That(someTest, Is.True);
         }
+
+        class UndeclaredSomeEngine : Engine
+        {
+            public override void Update(float dt)
+            {
+                someTest = this.Some<MockMessage>();
+            }
+        }
+
+        [Test]
+        public void IllegalSome()
+        {
+            var worldBuilder = new WorldBuilder();
+            worldBuilder.AddEngine<EmitMockMessageEngine>();
+            worldBuilder.AddEngine<UndeclaredSomeEngine>();
+
+            var world = worldBuilder.Build();
+
+            Assert.Throws<IllegalMessageReadException>(() => world.Update(0.01f));
+        }
     }
 }