diff --git a/build/dependencies.props b/build/dependencies.props
index 3c71bd378d..1235e00530 100644
--- a/build/dependencies.props
+++ b/build/dependencies.props
@@ -6,7 +6,7 @@
     <NETStandardImplicitPackageVersion>2.0.0-*</NETStandardImplicitPackageVersion>
     <NETStandardLibraryNETFrameworkVersion>2.0.0-*</NETStandardLibraryNETFrameworkVersion>
     <RuntimeFrameworkVersion Condition="'$(TargetFramework)'=='netcoreapp2.0'">2.0.0-*</RuntimeFrameworkVersion>
-    <TestSdkVersion>15.3.0-*</TestSdkVersion>
-    <XunitVersion>2.3.0-beta2-*</XunitVersion>
+    <TestSdkVersion>15.3.0</TestSdkVersion>
+    <XunitVersion>2.3.0-beta4-build3742</XunitVersion>
   </PropertyGroup>
 </Project>
diff --git a/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/AuthenticationTests.cs b/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/AuthenticationTests.cs
index ebb092b746..87a712fa24 100644
--- a/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/AuthenticationTests.cs
+++ b/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/AuthenticationTests.cs
@@ -36,7 +36,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys
             {
                 var response = await SendRequestAsync(address);
                 Assert.Equal(HttpStatusCode.OK, response.StatusCode);
-                Assert.Equal(0, response.Headers.WwwAuthenticate.Count);
+                Assert.Empty(response.Headers.WwwAuthenticate);
             }
         }
 
@@ -186,7 +186,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys
             {
                 var response = await SendRequestAsync(address);
                 Assert.Equal(HttpStatusCode.OK, response.StatusCode);
-                Assert.Equal(0, response.Headers.WwwAuthenticate.Count);
+                Assert.Empty(response.Headers.WwwAuthenticate);
             }
         }
 
@@ -306,12 +306,8 @@ namespace Microsoft.AspNetCore.Server.HttpSys
             }
         }
 
-        [ConditionalTheory]
-        [InlineData(AuthenticationSchemes.Negotiate)]
-        [InlineData(AuthenticationSchemes.NTLM)]
-        // [InlineData(AuthenticationSchemes.Digest)]
-        [InlineData(AuthenticationSchemes.Basic)]
-        public async Task AuthTypes_Forbid_Forbidden(AuthenticationSchemes authType)
+        [ConditionalFact]
+        public async Task AuthTypes_Forbid_Forbidden()
         {
             var authTypes = AuthenticationSchemes.Negotiate | AuthenticationSchemes.NTLM | /*AuthenticationSchemes.Digest |*/ AuthenticationSchemes.Basic;
             using (var server = Utilities.CreateDynamicHost(authTypes, AllowAnoymous, out var address, httpContext =>
@@ -324,7 +320,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys
             {
                 var response = await SendRequestAsync(address);
                 Assert.Equal(HttpStatusCode.Forbidden, response.StatusCode);
-                Assert.Equal(0, response.Headers.WwwAuthenticate.Count);
+                Assert.Empty(response.Headers.WwwAuthenticate);
             }
         }
 
@@ -345,7 +341,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys
             {
                 var response = await SendRequestAsync(address, useDefaultCredentials: true);
                 Assert.Equal(HttpStatusCode.Unauthorized, response.StatusCode);
-                Assert.Equal(1, response.Headers.WwwAuthenticate.Count);
+                Assert.Single(response.Headers.WwwAuthenticate);
                 Assert.Equal(authType.ToString(), response.Headers.WwwAuthenticate.First().Scheme);
             }
         }
diff --git a/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/AuthenticationTests.cs b/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/AuthenticationTests.cs
index 13c75bbfd2..ac7cb7056e 100644
--- a/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/AuthenticationTests.cs
+++ b/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/AuthenticationTests.cs
@@ -37,7 +37,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys.Listener
 
                 var response = await responseTask;
                 Assert.Equal(HttpStatusCode.OK, response.StatusCode);
-                Assert.Equal(0, response.Headers.WwwAuthenticate.Count);
+                Assert.Empty(response.Headers.WwwAuthenticate);
             }
         }
 
diff --git a/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/ResponseCachingTests.cs b/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/ResponseCachingTests.cs
index 1ed657515e..b3bc680e72 100644
--- a/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/ResponseCachingTests.cs
+++ b/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/ResponseCachingTests.cs
@@ -1083,7 +1083,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys.Listener
                 response = await SendRequestAsync(address, "GET", "Range", "bytes=0-10,15-20");
                 Assert.Equal(206, (int)response.StatusCode);
                 Assert.Equal("1", response.Headers.GetValues("x-request-count").FirstOrDefault());
-                Assert.True(response.Content.Headers.GetValues("content-type").First().StartsWith("multipart/byteranges;"));
+                Assert.StartsWith("multipart/byteranges;", response.Content.Headers.GetValues("content-type").First());
             }
         }
 
@@ -1145,7 +1145,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys.Listener
                 response = await SendRequestAsync(address, "GET", "Range", "bytes=0-" + (rangeLength - 1) + "," + rangeLength + "-" + (rangeLength + rangeLength - 1), HttpCompletionOption.ResponseHeadersRead);
                 Assert.Equal(206, (int)response.StatusCode);
                 Assert.Equal("1", response.Headers.GetValues("x-request-count").FirstOrDefault());
-                Assert.True(response.Content.Headers.GetValues("content-type").First().StartsWith("multipart/byteranges;"));
+                Assert.StartsWith("multipart/byteranges;", response.Content.Headers.GetValues("content-type").First());
             }
         }
 
diff --git a/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/ResponseHeaderTests.cs b/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/ResponseHeaderTests.cs
index 66ecbd7e19..86b377e7e3 100644
--- a/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/ResponseHeaderTests.cs
+++ b/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/ResponseHeaderTests.cs
@@ -40,7 +40,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys.Listener
                 Assert.False(response.Headers.TransferEncodingChunked.HasValue);
                 Assert.True(response.Headers.Date.HasValue);
                 Assert.Equal("Microsoft-HTTPAPI/2.0", response.Headers.Server.ToString());
-                Assert.Equal(1, response.Content.Headers.Count());
+                Assert.Single(response.Content.Headers);
                 Assert.Equal(0, response.Content.Headers.ContentLength);
             }
         }
@@ -63,7 +63,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys.Listener
                 Assert.True(response.Headers.ConnectionClose.Value);
                 Assert.True(response.Headers.Date.HasValue);
                 Assert.Equal("Microsoft-HTTPAPI/2.0", response.Headers.Server.ToString());
-                Assert.Equal(1, response.Content.Headers.Count());
+                Assert.Single(response.Content.Headers);
                 Assert.Equal(0, response.Content.Headers.ContentLength);
             }
         }
@@ -86,7 +86,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys.Listener
                 Assert.True(response.Headers.Date.HasValue);
                 Assert.Equal("Microsoft-HTTPAPI/2.0", response.Headers.Server.ToString());
                 Assert.False(response.Content.Headers.Contains("Content-Length"));
-                Assert.Equal(0, response.Content.Headers.Count());
+                Assert.Empty(response.Content.Headers);
 
                 // Send a second request to check that the connection wasn't corrupted.
                 responseTask = SendHeadRequestAsync(address);
@@ -115,7 +115,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys.Listener
                 Assert.True(response.Headers.Date.HasValue);
                 Assert.Equal("Microsoft-HTTPAPI/2.0", response.Headers.Server.ToString());
                 Assert.False(response.Content.Headers.Contains("Content-Length"));
-                Assert.Equal(0, response.Content.Headers.Count());
+                Assert.Empty(response.Content.Headers);
 
                 // Send a second request to check that the connection wasn't corrupted.
                 responseTask = SendHeadRequestAsync(address);
@@ -143,7 +143,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys.Listener
                 Assert.False(response.Headers.TransferEncodingChunked.HasValue);
                 Assert.True(response.Headers.Date.HasValue);
                 Assert.Equal("Microsoft-HTTPAPI/2.0", response.Headers.Server.ToString());
-                Assert.Equal(1, response.Content.Headers.Count());
+                Assert.Single(response.Content.Headers);
                 Assert.Equal(20, response.Content.Headers.ContentLength);
 
                 // Send a second request to check that the connection wasn't corrupted.
@@ -173,7 +173,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys.Listener
                 Assert.True(response.Headers.Date.HasValue);
                 Assert.Equal("Microsoft-HTTPAPI/2.0", response.Headers.Server.ToString());
                 Assert.False(response.Content.Headers.Contains("Content-Length"));
-                Assert.Equal(0, response.Content.Headers.Count());
+                Assert.Empty(response.Content.Headers);
             }
         }
 
@@ -196,7 +196,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys.Listener
                 Assert.True(response.Headers.Date.HasValue);
                 Assert.Equal("Microsoft-HTTPAPI/2.0", response.Headers.Server.ToString());
                 Assert.False(response.Content.Headers.Contains("Content-Length"));
-                Assert.Equal(0, response.Content.Headers.Count());
+                Assert.Empty(response.Content.Headers);
 
                 // Send a second request to check that the connection wasn't corrupted.
                 responseTask = SendHeadRequestAsync(address);
@@ -414,7 +414,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys.Listener
                 Assert.Equal(2, response.Headers.GetValues("Custom1").Count());
                 Assert.Equal("value1a", response.Headers.GetValues("Custom1").First());
                 Assert.Equal("value1b", response.Headers.GetValues("Custom1").Skip(1).First());
-                Assert.Equal(1, response.Headers.GetValues("Custom2").Count());
+                Assert.Single(response.Headers.GetValues("Custom2"));
                 Assert.Equal("value2a, value2b", response.Headers.GetValues("Custom2").First());
             }
         }
@@ -450,7 +450,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys.Listener
                 Assert.Equal(2, response.Headers.GetValues("Custom1").Count());
                 Assert.Equal("value1a", response.Headers.GetValues("Custom1").First());
                 Assert.Equal("value1b", response.Headers.GetValues("Custom1").Skip(1).First());
-                Assert.Equal(1, response.Headers.GetValues("Custom2").Count());
+                Assert.Single(response.Headers.GetValues("Custom2"));
                 Assert.Equal("value2a, value2b", response.Headers.GetValues("Custom2").First());
             }
         }
diff --git a/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/ResponseSendFileTests.cs b/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/ResponseSendFileTests.cs
index fb0b739295..a24bd3d4ac 100644
--- a/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/ResponseSendFileTests.cs
+++ b/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/Listener/ResponseSendFileTests.cs
@@ -203,7 +203,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys.Listener
                 IEnumerable<string> contentLength;
                 Assert.False(response.Content.Headers.TryGetValues("content-length", out contentLength), "Content-Length");
                 Assert.True(response.Headers.TransferEncodingChunked.Value);
-                Assert.Equal(0, (await response.Content.ReadAsByteArrayAsync()).Length);
+                Assert.Empty((await response.Content.ReadAsByteArrayAsync()));
             }
         }
 
@@ -299,7 +299,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys.Listener
                 Assert.True(response.Content.Headers.TryGetValues("content-length", out contentLength), "Content-Length");
                 Assert.Equal("0", contentLength.First());
                 Assert.Null(response.Headers.TransferEncodingChunked);
-                Assert.Equal(0, (await response.Content.ReadAsByteArrayAsync()).Length);
+                Assert.Empty((await response.Content.ReadAsByteArrayAsync()));
             }
         }
 
diff --git a/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/ResponseHeaderTests.cs b/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/ResponseHeaderTests.cs
index 0b169e906e..bec341b50f 100644
--- a/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/ResponseHeaderTests.cs
+++ b/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/ResponseHeaderTests.cs
@@ -32,7 +32,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys
                 Assert.False(response.Headers.TransferEncodingChunked.HasValue);
                 Assert.True(response.Headers.Date.HasValue);
                 Assert.Equal("Microsoft-HTTPAPI/2.0", response.Headers.Server.ToString());
-                Assert.Equal(1, response.Content.Headers.Count());
+                Assert.Single(response.Content.Headers);
                 Assert.Equal(0, response.Content.Headers.ContentLength);
             }
         }
@@ -224,7 +224,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys
                 Assert.Equal(2, response.Headers.GetValues("Custom1").Count());
                 Assert.Equal("value1a", response.Headers.GetValues("Custom1").First());
                 Assert.Equal("value1b", response.Headers.GetValues("Custom1").Skip(1).First());
-                Assert.Equal(1, response.Headers.GetValues("Custom2").Count());
+                Assert.Single(response.Headers.GetValues("Custom2"));
                 Assert.Equal("value2a, value2b", response.Headers.GetValues("Custom2").First());
             }
         }
@@ -254,7 +254,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys
                 Assert.Equal(2, response.Headers.GetValues("Custom1").Count());
                 Assert.Equal("value1a", response.Headers.GetValues("Custom1").First());
                 Assert.Equal("value1b", response.Headers.GetValues("Custom1").Skip(1).First());
-                Assert.Equal(1, response.Headers.GetValues("Custom2").Count());
+                Assert.Single(response.Headers.GetValues("Custom2"));
                 Assert.Equal("value2a, value2b", response.Headers.GetValues("Custom2").First());
             }
         }
diff --git a/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/ResponseSendFileTests.cs b/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/ResponseSendFileTests.cs
index 02117c6b53..d3a8c5e5d0 100644
--- a/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/ResponseSendFileTests.cs
+++ b/test/Microsoft.AspNetCore.Server.HttpSys.FunctionalTests/ResponseSendFileTests.cs
@@ -253,7 +253,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys
                 IEnumerable<string> contentLength;
                 Assert.False(response.Content.Headers.TryGetValues("content-length", out contentLength), "Content-Length");
                 Assert.True(response.Headers.TransferEncodingChunked.Value);
-                Assert.Equal(0, (await response.Content.ReadAsByteArrayAsync()).Length);
+                Assert.Empty((await response.Content.ReadAsByteArrayAsync()));
             }
         }
 
@@ -316,7 +316,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys
                 Assert.True(response.Content.Headers.TryGetValues("content-length", out contentLength), "Content-Length");
                 Assert.Equal("0", contentLength.First());
                 Assert.Null(response.Headers.TransferEncodingChunked);
-                Assert.Equal(0, (await response.Content.ReadAsByteArrayAsync()).Length);
+                Assert.Empty((await response.Content.ReadAsByteArrayAsync()));
             }
         }