Add temporary test to verify NTLM and Negotiate connections from all …

…platforms

Notably this is expected to fail on Android and tvOS where GSSAPI is not available.

The test machine is single purpose virtual machine running in Azure with clean Windows Server 2019 installation and all the patches. It hosts IIS with single static page behind an NT authentication. The test account and the machine itself is disposable and does NOT contain any sensitive data. Nevertheless I don't expect this test to be merged.

src/libraries/System.Net.Http/tests/FunctionalTests/NtAuthTests.cs

@@ -160,5 +160,23 @@ public async Task PostAsync_NtAuthServer_UseExpect100Header_Success(bool ntlm, i
                 }
             }
         }
+
+        [Theory]
+        [InlineData("NTLM")]
+        [InlineData("Negotiate")]
+        public async Task AuthTest(string authType)
+        {
+            var testUri = new Uri("http://emclientntlm.westus.cloudapp.azure.com/");
+            var networkCredential = new NetworkCredential("user1", "PLACEHOLDERcorrect20", "emclientntlm");
+
+            using var socketsHandler = new SocketsHttpHandler();
+            var credentialCache = new CredentialCache();
+            credentialCache.Add(testUri, authType, networkCredential);
+            socketsHandler.Credentials = credentialCache;
+
+            using var client = new HttpClient(socketsHandler);
+            var result = await client.GetAsync(testUri);
+            Assert.True(result.IsSuccessStatusCode);
+        }
     }
 }