now returns response content headers

src/Ocelot/Headers/RemoveOutputHeaders.cs

@@ -3,6 +3,8 @@ using Ocelot.Responses;
 
 namespace Ocelot.Headers
 {
+    using System;
+
     public class RemoveOutputHeaders : IRemoveOutputHeaders
     {
         /// <summary>
@@ -10,14 +12,13 @@ namespace Ocelot.Headers
         /// in a given context such as transfer encoding chunked when ASP.NET is not
         /// returning the response in this manner
         /// </summary>
-        private readonly string[] _unsupportedHeaders = 
+        private readonly string[] _unsupportedRequestHeaders = 
         {
             "Transfer-Encoding"
         };
-
         public Response Remove(HttpResponseHeaders headers)
         {
-            foreach (var unsupported in _unsupportedHeaders)
+            foreach (var unsupported in _unsupportedRequestHeaders)
             {
                 headers.Remove(unsupported);
             }

src/Ocelot/Responder/HttpContextResponder.cs

@@ -9,6 +9,8 @@ using Ocelot.Responses;
 
 namespace Ocelot.Responder
 {
+    using System.Collections.Generic;
+
     /// <summary>
     /// Cannot unit test things in this class due to methods not being implemented
     /// on .net concretes used for testing
@@ -28,12 +30,17 @@ namespace Ocelot.Responder
 
             foreach (var httpResponseHeader in response.Headers)
             {
-                context.Response.Headers.Add(httpResponseHeader.Key, new StringValues(httpResponseHeader.Value.ToArray()));
+                AddHeaderIfDoesntExist(context, httpResponseHeader);
+            }
+
+            foreach (var httpResponseHeader in response.Content.Headers)
+            {
+                AddHeaderIfDoesntExist(context, httpResponseHeader);
             }
 
             var content = await response.Content.ReadAsStreamAsync();
 
-            context.Response.Headers.Add("Content-Length", new[] { content.Length.ToString() });
+            AddHeaderIfDoesntExist(context, new KeyValuePair<string, IEnumerable<string>>("Content-Length", new []{ content.Length.ToString() }) );
 
             context.Response.OnStarting(state =>
             {
@@ -54,6 +61,14 @@ namespace Ocelot.Responder
             return new OkResponse();       
         }
 
+        private static void AddHeaderIfDoesntExist(HttpContext context, KeyValuePair<string, IEnumerable<string>> httpResponseHeader)
+        {
+            if (!context.Response.Headers.ContainsKey(httpResponseHeader.Key))
+            {
+                context.Response.Headers.Add(httpResponseHeader.Key, new StringValues(httpResponseHeader.Value.ToArray()));
+            }
+        }
+
         public async Task<Response> SetErrorResponseOnContext(HttpContext context, int statusCode)
         {
             context.Response.OnStarting(x =>

test/Ocelot.UnitTests/Headers/RemoveHeadersTests.cs

@@ -7,13 +7,13 @@ using Xunit;
 
 namespace Ocelot.UnitTests.Headers
 {
-    public class RemoveHeaders
+    public class RemoveHeadersTests
     {
         private HttpResponseHeaders _headers;
         private readonly Ocelot.Headers.RemoveOutputHeaders _removeOutputHeaders;
         private Response _result;
 
-        public RemoveHeaders()
+        public RemoveHeadersTests()
         {
             _removeOutputHeaders = new Ocelot.Headers.RemoveOutputHeaders();
         }