System.Net.Security.Tests.NegotiateStreamKerberosTest.VerifyAuthentication C# (CSharp) Method

        private async Task VerifyAuthentication(NetworkCredential credential)
        {
            string serverName = Configuration.Security.NegotiateServer.Host;
            int port = Configuration.Security.NegotiateServer.Port;
            string serverSPN = "HOST/" + serverName;
            bool isLocalhost = await IsLocalHost(serverName);
            
            string expectedAuthenticationType = "Kerberos";
            bool mutualAuthenitcated = true;

            if (credential == CredentialCache.DefaultNetworkCredentials && isLocalhost)
            {
                expectedAuthenticationType = "NTLM";
            }
            else if (credential != CredentialCache.DefaultNetworkCredentials && 
                (string.IsNullOrEmpty(credential.UserName) || string.IsNullOrEmpty(credential.Password)))
            {
                // Anonymous authentication.
                expectedAuthenticationType = "NTLM";
                mutualAuthenitcated = false;
            }

            using (var client = new TcpClient())
            {
                await client.ConnectAsync(serverName, port);

                NetworkStream clientStream = client.GetStream();
                using (var auth = new NegotiateStream(clientStream, leaveInnerStreamOpen:false))
                {
                    await auth.AuthenticateAsClientAsync(
                        credential,
                        serverSPN,
                        ProtectionLevel.EncryptAndSign,
                        System.Security.Principal.TokenImpersonationLevel.Identification);

                    Assert.Equal(expectedAuthenticationType, auth.RemoteIdentity.AuthenticationType);
                    Assert.Equal(serverSPN, auth.RemoteIdentity.Name);

                    Assert.Equal(true, auth.IsAuthenticated);
                    Assert.Equal(true, auth.IsEncrypted);
                    Assert.Equal(mutualAuthenitcated, auth.IsMutuallyAuthenticated);
                    Assert.Equal(true, auth.IsSigned);

                    // Send a message to the server. Encode the test data into a byte array.
                    byte[] message = Encoding.UTF8.GetBytes("Hello from the client.");
                    await auth.WriteAsync(message, 0, message.Length);
                }
            }
        }