Additional unit tests related to #965 to make sure decorators can be applied more than once if intentional.

Author: alexmg

test/Autofac.Specification.Test/Features/DecoratorTests.cs

@@ -276,10 +276,47 @@ public void DecoratorAppliedOnlyOnceToComponentWithExternalRegistrySource()
 
             var scope = container.BeginLifetimeScope(b => { });
             var service = scope.Resolve<IDecoratedService>();
+
             Assert.IsType<DecoratorA>(service);
             Assert.IsType<ImplementorA>(service.Decorated);
         }
 
+        [Fact]
+        public void DecoratorCanBeAppliedTwice()
+        {
+            var builder = new ContainerBuilder();
+            builder.RegisterType<ImplementorA>().As<IDecoratedService>();
+            builder.RegisterDecorator<DecoratorA, IDecoratedService>();
+            builder.RegisterDecorator<DecoratorA, IDecoratedService>();
+            var container = builder.Build();
+
+            var service = container.Resolve<IDecoratedService>();
+
+            Assert.IsType<DecoratorA>(service);
+            Assert.IsType<DecoratorA>(service.Decorated);
+            Assert.IsType<ImplementorA>(service.Decorated.Decorated);
+        }
+
+        [Fact]
+        public void DecoratorCanBeAppliedTwiceInChildLifetimeScope()
+        {
+            var builder = new ContainerBuilder();
+            builder.RegisterType<ImplementorA>().As<IDecoratedService>();
+            builder.RegisterDecorator<DecoratorA, IDecoratedService>();
+            var container = builder.Build();
+
+            var scope = container.BeginLifetimeScope(b => b.RegisterDecorator<DecoratorA, IDecoratedService>());
+            var scopeInstance = scope.Resolve<IDecoratedService>();
+
+            Assert.IsType<DecoratorA>(scopeInstance);
+            Assert.IsType<DecoratorA>(scopeInstance.Decorated);
+            Assert.IsType<ImplementorA>(scopeInstance.Decorated.Decorated);
+
+            var rootInstance = container.Resolve<IDecoratedService>();
+            Assert.IsType<DecoratorA>(rootInstance);
+            Assert.IsType<ImplementorA>(rootInstance.Decorated);
+        }
+
         [Fact]
         public void DecoratorCanBeAppliedToServiceRegisteredInChildLifetimeScope()
         {

test/Autofac.Test/Features/Decorators/OpenGenericDecoratorTests.cs

@@ -550,6 +550,42 @@ public void DecoratorAppliedOnlyOnceToComponentWithExternalRegistrySource()
             Assert.IsType<ImplementorA<int>>(service.Decorated);
         }
 
+        [Fact]
+        public void DecoratorCanBeAppliedTwice()
+        {
+            var builder = new ContainerBuilder();
+            builder.RegisterGeneric(typeof(ImplementorA<>)).As(typeof(IDecoratedService<>));
+            builder.RegisterGenericDecorator(typeof(DecoratorA<>), typeof(IDecoratedService<>));
+            builder.RegisterGenericDecorator(typeof(DecoratorA<>), typeof(IDecoratedService<>));
+            var container = builder.Build();
+
+            var service = container.Resolve<IDecoratedService<int>>();
+
+            Assert.IsType<DecoratorA<int>>(service);
+            Assert.IsType<DecoratorA<int>>(service.Decorated);
+            Assert.IsType<ImplementorA<int>>(service.Decorated.Decorated);
+        }
+
+        [Fact]
+        public void DecoratorCanBeAppliedTwiceInChildLifetimeScope()
+        {
+            var builder = new ContainerBuilder();
+            builder.RegisterGeneric(typeof(ImplementorA<>)).As(typeof(IDecoratedService<>));
+            builder.RegisterGenericDecorator(typeof(DecoratorA<>), typeof(IDecoratedService<>));
+            var container = builder.Build();
+
+            var scope = container.BeginLifetimeScope(b => b.RegisterGenericDecorator(typeof(DecoratorA<>), typeof(IDecoratedService<>)));
+            var scopeInstance = scope.Resolve<IDecoratedService<int>>();
+
+            Assert.IsType<DecoratorA<int>>(scopeInstance);
+            Assert.IsType<DecoratorA<int>>(scopeInstance.Decorated);
+            Assert.IsType<ImplementorA<int>>(scopeInstance.Decorated.Decorated);
+
+            var rootInstance = container.Resolve<IDecoratedService<int>>();
+            Assert.IsType<DecoratorA<int>>(rootInstance);
+            Assert.IsType<ImplementorA<int>>(rootInstance.Decorated);
+        }
+
         [Fact]
         public void DecoratorCanBeAppliedToServiceRegisteredInChildLifetimeScope()
         {