#298 initial hacking around better aggregation (#310)

* #298 initial hacking around better aggregation

* #298 bit more hacking around

* #298 abstraction over httpresponsemessage

* #298 tidying up

* #298 docs

* #298 missed this

test/Ocelot.UnitTests/Middleware/ResponseAggregatorFactoryTests.cs

@@ -0,0 +1,64 @@
+namespace Ocelot.UnitTests.Middleware
+{
+    using Moq;
+    using Ocelot.Configuration.Builder;
+    using Ocelot.Middleware.Multiplexer;
+    using Shouldly;
+    using Xunit;
+    using Ocelot.Configuration;
+    using TestStack.BDDfy;
+
+    public class ResponseAggregatorFactoryTests
+    {
+        private readonly InMemoryResponseAggregatorFactory _factory;
+        private Mock<IDefinedAggregatorProvider> _provider;
+        private ReRoute _reRoute;
+        private IResponseAggregator _aggregator;
+
+        public ResponseAggregatorFactoryTests()
+        {
+            _provider = new Mock<IDefinedAggregatorProvider>();
+            _factory = new InMemoryResponseAggregatorFactory(_provider.Object);
+        }
+        
+        [Fact]
+        public void should_return_simple_json_aggregator()
+        {
+            var reRoute = new ReRouteBuilder()
+                .Build();
+
+            this.Given(_ => GivenReRoute(reRoute))
+                .When(_ => WhenIGet())
+                .Then(_ => ThenTheAggregatorIs<SimpleJsonResponseAggregator>())
+                .BDDfy();
+        }
+
+        [Fact]
+        public void should_return_user_defined_aggregator()
+        {
+            var reRoute = new ReRouteBuilder()
+                .WithAggregator("doesntmatter")
+                .Build();
+
+            this.Given(_ => GivenReRoute(reRoute))
+                .When(_ => WhenIGet())
+                .Then(_ => ThenTheAggregatorIs<UserDefinedResponseAggregator>())
+                .BDDfy();
+        }
+
+        private void GivenReRoute(ReRoute reRoute)
+        {
+            _reRoute = reRoute;
+        }
+
+        private void WhenIGet()
+        {
+            _aggregator = _factory.Get(_reRoute);
+        }
+
+        private void ThenTheAggregatorIs<T>()
+        {
+            _aggregator.ShouldBeOfType<T>();
+        }
+    }
+}