add test

Author: twsouthwick

src/Microsoft.Data.SqlClient/tests/ManualTests/SQL/KerberosTests/KerberosTest.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
+using System.Buffers;
 using System.Collections;
 using System.Collections.Generic;
 using Xunit;
@@ -24,6 +26,43 @@ public void IsKerBerosSetupTestAsync(string connectionStr)
             Assert.True(reader.Read(), "Expected to receive one row data");
             Assert.Equal("KERBEROS", reader.GetString(0));
         }
+
+        [PlatformSpecific(TestPlatforms.AnyUnix)]
+        [ConditionalTheory(typeof(DataTestUtility), nameof(DataTestUtility.IsKerberosTest))]
+        [ClassData(typeof(ConnectionStringsProvider))]
+        public void CustomSspiContextGeneratorTest(string connectionStr)
+        {
+            KerberosTicketManagemnt.Init(DataTestUtility.KerberosDomainUser, DataTestUtility.KerberosDomainPassword);
+
+            using SqlConnection conn = new(connectionStr)
+            {
+                SspiContextProvider = new TestSspiContextProvider(),
+            };
+
+            try
+            {
+                conn.Open();
+                using SqlCommand command = new("SELECT auth_scheme from sys.dm_exec_connections where session_id = @@spid", conn);
+                using SqlDataReader reader = command.ExecuteReader();
+
+                Assert.Fail("Expected to use custom SSPI context provider");
+            }
+            catch (SspiTestException)
+            {
+            }
+        }
+
+        private sealed class TestSspiContextProvider : SspiContextProvider
+        {
+            protected override bool GenerateContext(ReadOnlySpan<byte> incomingBlob, IBufferWriter<byte> outgoingBlobWriter, SspiAuthenticationParameters authParams)
+            {
+                throw new SspiTestException();
+            }
+        }
+
+        private sealed class SspiTestException : Exception
+        {
+        }
     }
 
     public class ConnectionStringsProvider : IEnumerable<object[]>