- add factory validation

LightweightIocContainer/Registrations/RegistrationBase.cs

@@ -111,8 +111,9 @@ namespace LightweightIocContainer.Registrations
         public IRegistrationBase WithFactory<TFactory>()
         {
             TypedFactory<TFactory> factory = new(_container);
-            
             Factory = factory;
+            
+            ValidateFactory();
             _container.RegisterFactory(factory);
             
             return this;
@@ -127,9 +128,17 @@ namespace LightweightIocContainer.Registrations
         public IRegistrationBase WithFactory<TFactoryInterface, TFactoryImplementation>() where TFactoryImplementation : TFactoryInterface
         {
             Factory = new CustomTypedFactory<TFactoryInterface>();
+            ValidateFactory();
+            
             _container.Register<TFactoryInterface, TFactoryImplementation>();
 
             return this;
         }
+
+        private void ValidateFactory()
+        {
+            if (Factory?.CreateMethods.Any(c => c.ReturnType == InterfaceType) != true)
+                throw new InvalidFactoryRegistrationException($"No create method that can create {InterfaceType}.");
+        }
     }
 }

Test.LightweightIocContainer/FluentFactoryRegistrationTest.cs

@@ -78,6 +78,12 @@ namespace Test.LightweightIocContainer
             public void ClearMultitonInstance<T>() => throw new System.NotImplementedException();
         }
         
+        [UsedImplicitly]
+        public interface ITestFactoryWrongReturn
+        {
+            public MultitonScope Create();
+        }
+        
         public class MultitonScope
         {
 
@@ -225,5 +231,9 @@ namespace Test.LightweightIocContainer
             Assert.AreNotSame(resolvedTest2, resolvedTest4);
             Assert.AreNotSame(resolvedTest3, resolvedTest5);
         }
+
+        [Test]
+        public void TestInvalidCreateMethodReturnType() => 
+            Assert.Throws<InvalidFactoryRegistrationException>(() => _iocContainer.Register<ITest, Test>().WithFactory<ITestFactoryWrongReturn>());
     }
 }