func tryAuth(t *testing.T, config *ClientConfig) error {
	c1, c2, err := netPipe()
	if err != nil {
		t.Fatalf("netPipe: %v", err)
	}
	defer c1.Close()
	defer c2.Close()
	certChecker := CertChecker{
		IsUserAuthority: func(k PublicKey) bool {
			return bytes.Equal(k.Marshal(), testPublicKeys["ecdsa"].Marshal())
		},
		UserKeyFallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
			if conn.User() == "testuser" && bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
				return nil, nil
			}
			return nil, fmt.Errorf("pubkey for %q not acceptable", conn.User())
		},
		IsRevoked: func(c *Certificate) bool {
			return c.Serial == 666
		},
	}
	serverConfig := &ServerConfig{
		PasswordCallback: func(conn ConnMetadata, pass []byte) (*Permissions, error) {
			if conn.User() == "testuser" && string(pass) == clientPassword {
				return nil, nil
			}
			return nil, errors.New("password auth failed")
		},
		PublicKeyCallback: certChecker.Authenticate,
		KeyboardInteractiveCallback: func(conn ConnMetadata, challenge KeyboardInteractiveChallenge) (*Permissions, error) {
			ans, err := challenge("user",
				"instruction",
				[]string{"question1", "question2"},
				[]bool{true, true})
			if err != nil {
				return nil, err
			}
			ok := conn.User() == "testuser" && ans[0] == "answer1" && ans[1] == "answer2"
			if ok {
				challenge("user", "motd", nil, nil)
				return nil, nil
			}
			return nil, errors.New("keyboard-interactive failed")
		},
	}
	serverConfig.AddHostKey(testSigners["rsa"])
	go newServer(c1, serverConfig)
	_, _, _, err = NewClientConn(c2, "", config)
	return err
}
tryAuth runs a handshake with a given config against an SSH server
with config serverConfig
package ssh
import (
	"bytes"
	"crypto/rand"
	"errors"
	"fmt"
	"os"
	"strings"
	"testing"
)
type keyboardInteractive map[string]string
func (cr keyboardInteractive) Challenge(user string, instruction string, questions []string, echos []bool) ([]string, error) {
	var answers []string
	for _, q := range questions {
		answers = append(answers, cr[q])
	}
	return answers, nil
}
var clientPassword = "tiger"