diff --git a/test/Microsoft.AspNetCore.Mvc.Formatters.Xml.Test/XmlDataContractSerializerInputFormatterTest.cs b/test/Microsoft.AspNetCore.Mvc.Formatters.Xml.Test/XmlDataContractSerializerInputFormatterTest.cs
index 4673dc3ec9..2c10ba7b09 100644
--- a/test/Microsoft.AspNetCore.Mvc.Formatters.Xml.Test/XmlDataContractSerializerInputFormatterTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.Formatters.Xml.Test/XmlDataContractSerializerInputFormatterTest.cs
@@ -54,8 +54,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [InlineData("application/xml", true)]
         [InlineData("application/*", false)]
         [InlineData("*/*", false)]
@@ -91,8 +90,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public void XmlDataContractSerializer_CachesSerializerForType()
         {
             // Arrange
@@ -137,8 +135,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ReadAsync_ReadsSimpleTypes()
         {
             // Arrange
@@ -166,8 +163,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ReadAsync_ReadsComplexTypes()
         {
             // Arrange
@@ -198,8 +194,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ReadAsync_ReadsWhenMaxDepthIsModified()
         {
             // Arrange
@@ -274,8 +269,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ReadAsync_VerifyStreamIsOpenAfterRead()
         {
             // Arrange
@@ -296,8 +290,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ReadAsync_FallsbackToUTF8_WhenCharSet_NotInContentType()
         {
             // Arrange
@@ -325,8 +318,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ReadAsync_UsesContentTypeCharSet_ToReadStream()
         {
             // Arrange
@@ -358,8 +350,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ReadAsync_IgnoresBOMCharacters()
         {
             // Arrange
@@ -392,8 +383,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ReadAsync_AcceptsUTF16Characters()
         {
             // Arrange
@@ -432,8 +422,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ReadAsync_ThrowsWhenNotConfiguredWithRootName()
         {
             // Arrange
@@ -453,8 +442,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ReadAsync_ReadsWhenConfiguredWithRootName()
         {
             // Arrange
@@ -492,8 +480,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ReadAsync_ThrowsWhenNotConfiguredWithKnownTypes()
         {
             // Arrange
@@ -514,8 +501,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ReadAsync_ReadsWhenConfiguredWithKnownTypes()
         {
             // Arrange
diff --git a/test/Microsoft.AspNetCore.Mvc.Formatters.Xml.Test/XmlDataContractSerializerOutputFormatterTest.cs b/test/Microsoft.AspNetCore.Mvc.Formatters.Xml.Test/XmlDataContractSerializerOutputFormatterTest.cs
index ba9de64a2a..40323a28cb 100644
--- a/test/Microsoft.AspNetCore.Mvc.Formatters.Xml.Test/XmlDataContractSerializerOutputFormatterTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.Formatters.Xml.Test/XmlDataContractSerializerOutputFormatterTest.cs
@@ -94,8 +94,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [MemberData(nameof(BasicTypeValues))]
         public async Task WriteAsync_CanWriteBasicTypes(object input, string expectedOutput)
         {
@@ -115,8 +114,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public void XmlDataContractSerializer_CachesSerializerForType()
         {
             // Arrange
@@ -135,8 +133,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public void DefaultConstructor_ExpectedWriterSettings_Created()
         {
             // Arrange and Act
@@ -151,8 +148,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task SuppliedWriterSettings_TakeAffect()
         {
             // Arrange
@@ -179,8 +175,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task WriteAsync_WritesSimpleTypes()
         {
             // Arrange
@@ -204,8 +199,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task WriteAsync_WritesComplexTypes()
         {
             // Arrange
@@ -239,8 +233,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task WriteAsync_WritesOnModifiedWriterSettings()
         {
             // Arrange
@@ -270,8 +263,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task WriteAsync_WritesUTF16Output()
         {
             // Arrange
@@ -300,8 +292,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task WriteAsync_WritesIndentedOutput()
         {
             // Arrange
@@ -326,8 +317,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task WriteAsync_VerifyBodyIsNotClosedAfterOutputIsWritten()
         {
             // Arrange
@@ -344,8 +334,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task WriteAsync_DoesntFlushOutputStream()
         {
             // Arrange
@@ -375,8 +364,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [MemberData(nameof(TypesForCanWriteResult))]
         public void CanWriteResult_ReturnsExpectedOutput(object input, Type declaredType, bool expectedOutput)
         {
@@ -403,8 +391,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [MemberData(nameof(TypesForGetSupportedContentTypes))]
         public void GetSupportedContentTypes_ReturnsSupportedTypes(Type type, object expectedOutput)
         {
@@ -428,11 +415,10 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
 #if !DNXCORE50
-        // DataContractSerializer in CoreCLR does not throw if the declared type is different from the type being
-        // serialized.
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        // DataContractSerializer in CoreCLR does not throw if the declared type is different from the type being
+        // serialized. Is this the same issue as aspnet/External#18???
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task WriteAsync_ThrowsWhenNotConfiguredWithKnownTypes()
         {
             // Arrange
@@ -467,8 +453,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
 #endif
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task WriteAsync_ThrowsWhenNotConfiguredWithPreserveReferences()
         {
             // Arrange
@@ -485,8 +470,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task WriteAsync_WritesWhenConfiguredWithRootName()
         {
             // Arrange
@@ -528,8 +512,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task WriteAsync_WritesWhenConfiguredWithKnownTypes()
         {
             // Arrange
@@ -574,8 +557,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task WriteAsync_WritesWhenConfiguredWithPreserveReferences()
         {
             // Arrange
diff --git a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/ApiExplorerTest.cs b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/ApiExplorerTest.cs
index e121481499..7711051f3a 100644
--- a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/ApiExplorerTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/ApiExplorerTest.cs
@@ -487,8 +487,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ApiExplorer_ResponseContentType_Unset()
         {
             // Arrange & Act
@@ -553,8 +552,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [InlineData("Controller", "text/xml", "Microsoft.AspNetCore.Mvc.Formatters.XmlDataContractSerializerOutputFormatter")]
         [InlineData("Action", "application/json", "Microsoft.AspNetCore.Mvc.Formatters.JsonOutputFormatter")]
         public async Task ApiExplorer_ResponseContentType_OverrideOnAction(
diff --git a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/ConsumesAttributeTests.cs b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/ConsumesAttributeTests.cs
index 18e162e3d6..8c04ff7ad3 100644
--- a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/ConsumesAttributeTests.cs
+++ b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/ConsumesAttributeTests.cs
@@ -6,7 +6,6 @@ using System.Net.Http;
 using System.Text;
 using System.Threading.Tasks;
 using BasicWebSite.Models;
-using Microsoft.AspNetCore.Mvc.Infrastructure;
 using Microsoft.AspNetCore.Testing.xunit;
 using Newtonsoft.Json;
 using Xunit;
@@ -100,8 +99,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task DerivedClassLevelAttribute_OveridesBaseClassLevel()
         {
             // Arrange
diff --git a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/ContentNegotiationTest.cs b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/ContentNegotiationTest.cs
index f03bd99478..5688a17712 100644
--- a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/ContentNegotiationTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/ContentNegotiationTest.cs
@@ -107,8 +107,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ProducesAttribute_WithTypeAndContentType_UsesContentType()
         {
             // Arrange
@@ -299,8 +298,7 @@ END:VCARD
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task XmlFormatter_SupportedMediaType_DoesNotChangeAcrossRequests()
         {
             // Arrange
diff --git a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/InputFormatterTests.cs b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/InputFormatterTests.cs
index eb56bc0298..d6980e556f 100644
--- a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/InputFormatterTests.cs
+++ b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/InputFormatterTests.cs
@@ -22,8 +22,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         public HttpClient Client { get; }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task CheckIfXmlInputFormatterIsBeingCalled()
         {
             // Arrange
diff --git a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/InputObjectValidationTests.cs b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/InputObjectValidationTests.cs
index 42e99ec106..d563b2cc2e 100644
--- a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/InputObjectValidationTests.cs
+++ b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/InputObjectValidationTests.cs
@@ -46,8 +46,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task CheckIfObjectIsDeserializedWithoutErrors()
         {
             // Arrange
diff --git a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/JsonOutputFormatterTests.cs b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/JsonOutputFormatterTests.cs
index 2d17bd5365..4842090b97 100644
--- a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/JsonOutputFormatterTests.cs
+++ b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/JsonOutputFormatterTests.cs
@@ -48,8 +48,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task SerializableErrorIsReturnedInExpectedFormat()
         {
             // Arrange
diff --git a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/RespectBrowserAcceptHeaderTests.cs b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/RespectBrowserAcceptHeaderTests.cs
index 147b131524..6390426326 100644
--- a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/RespectBrowserAcceptHeaderTests.cs
+++ b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/RespectBrowserAcceptHeaderTests.cs
@@ -41,8 +41,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [InlineData("application/xml,*/*;q=0.2")]
         [InlineData("application/xml,*/*")]
         public async Task AllMediaRangeAcceptHeader_ProducesAttributeIsHonored(string acceptHeader)
@@ -69,8 +68,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [InlineData("application/xml,*/*;q=0.2")]
         [InlineData("application/xml,*/*")]
         public async Task AllMediaRangeAcceptHeader_WithContentTypeHeader_ContentTypeIsIgnored(string acceptHeader)
@@ -101,8 +99,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [InlineData("application/xml,application/json;q=0.2")]
         [InlineData("application/xml,application/json")]
         public async Task AllMediaRangeAcceptHeader_WithExactMatch_ReturnsExpectedContent(string acceptHeader)
diff --git a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/SerializableErrorTests.cs b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/SerializableErrorTests.cs
index 6c86fd75dd..d277704f93 100644
--- a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/SerializableErrorTests.cs
+++ b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/SerializableErrorTests.cs
@@ -31,7 +31,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
                     "application/xml-xmlser"
                 };
 
-                // Mono issue - https://github.com/aspnet/External/issues/18
+                // Avoid aspnet/External#18, a DCS issue on Mono.
                 if (!TestPlatformHelper.IsMono)
                 {
                     data.Add("application/xml-dcs");
@@ -63,10 +63,8 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        // XmlSerializer test is disabled Mono.Xml2.XmlTextReader.ReadText is unable to read the XML.
-        // This is fixed in mono 4.3.0.
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        // Mono.Xml2.XmlTextReader.ReadText is unable to read the XML. Is this the same bug as aspnet/External#18???
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [InlineData("application/xml-xmlser")]
         [InlineData("application/xml-dcs")]
         public async Task PostedSerializableError_IsBound(string acceptHeader)
@@ -90,10 +88,8 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        // XmlSerializer test is disabled Mono.Xml2.XmlTextReader.ReadText is unable to read the XML.
-        // This is fixed in mono 4.3.0.
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        // Mono.Xml2.XmlTextReader.ReadText is unable to read the XML. Is this the same bug as aspnet/External#18???
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [InlineData("application/xml-xmlser")]
         [InlineData("application/xml-dcs")]
         public async Task IsReturnedInExpectedFormat(string acceptHeader)
diff --git a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/XmlDataContractSerializerFormattersWrappingTest.cs b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/XmlDataContractSerializerFormattersWrappingTest.cs
index 5bd38a326c..4656d5c3b0 100644
--- a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/XmlDataContractSerializerFormattersWrappingTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/XmlDataContractSerializerFormattersWrappingTest.cs
@@ -21,8 +21,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         public HttpClient Client { get; }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [InlineData("http://localhost/IEnumerable/ValueTypes")]
         [InlineData("http://localhost/IQueryable/ValueTypes")]
         public async Task CanWrite_ValueTypes(string url)
@@ -45,8 +44,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [InlineData("http://localhost/IEnumerable/NonWrappedTypes")]
         [InlineData("http://localhost/IQueryable/NonWrappedTypes")]
         public async Task CanWrite_NonWrappedTypes(string url)
@@ -69,8 +67,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [InlineData("http://localhost/IEnumerable/NonWrappedTypes_Empty")]
         [InlineData("http://localhost/IQueryable/NonWrappedTypes_Empty")]
         public async Task CanWrite_NonWrappedTypes_Empty(string url)
@@ -92,8 +89,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [InlineData("http://localhost/IEnumerable/NonWrappedTypes_NullInstance")]
         [InlineData("http://localhost/IQueryable/NonWrappedTypes_NullInstance")]
         public async Task CanWrite_NonWrappedTypes_NullInstance(string url)
@@ -115,8 +111,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [InlineData("http://localhost/IEnumerable/WrappedTypes")]
         [InlineData("http://localhost/IQueryable/WrappedTypes")]
         public async Task CanWrite_WrappedTypes(string url)
@@ -140,8 +135,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [InlineData("http://localhost/IEnumerable/WrappedTypes_Empty")]
         [InlineData("http://localhost/IQueryable/WrappedTypes_Empty")]
         public async Task CanWrite_WrappedTypes_Empty(string url)
@@ -163,8 +157,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalTheory]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         [InlineData("http://localhost/IEnumerable/WrappedTypes_NullInstance")]
         [InlineData("http://localhost/IQueryable/WrappedTypes_NullInstance")]
         public async Task CanWrite_WrappedTypes_NullInstance(string url)
@@ -186,8 +179,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task CanWrite_IEnumerableOf_SerializableErrors()
         {
             // Arrange
diff --git a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/XmlDataContractSerializerInputFormatterTest.cs b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/XmlDataContractSerializerInputFormatterTest.cs
index eec000aabf..e03578f4cd 100644
--- a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/XmlDataContractSerializerInputFormatterTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/XmlDataContractSerializerInputFormatterTest.cs
@@ -35,8 +35,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         public HttpClient Client { get; }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task ThrowsOnInvalidInput_AndAddsToModelState()
         {
             // Arrange
@@ -57,8 +56,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task RequiredDataIsProvided_AndModelIsBound_NoValidationErrors()
         {
             // Arrange
@@ -87,8 +85,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
 
         // Verifies that the model state has errors related to body model validation.
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mon, SkipReason = "aspnet/External#18, DCS issue on Mono"o)]
         public async Task DataMissingForRefereneceTypeProperties_AndModelIsBound_AndHasMixedValidationErrors()
         {
             // Arrange
diff --git a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/XmlOutputFormatterTests.cs b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/XmlOutputFormatterTests.cs
index cc9e8eb5be..4e5a25a96f 100644
--- a/test/Microsoft.AspNetCore.Mvc.FunctionalTests/XmlOutputFormatterTests.cs
+++ b/test/Microsoft.AspNetCore.Mvc.FunctionalTests/XmlOutputFormatterTests.cs
@@ -64,8 +64,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [ConditionalFact]
-        // Mono issue - https://github.com/aspnet/External/issues/18
-        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "aspnet/External#18, DCS issue on Mono")]
         public async Task XmlSerializerFailsAndDataContractSerializerIsCalled()
         {
             // Arrange