add a unit test using the test vector from the draft

internal/handshake/handshake_suite_test.go

@@ -3,6 +3,8 @@ package handshake
 import (
 	"crypto"
 	"crypto/cipher"
+	"encoding/hex"
+	"strings"
 
 	"github.com/alangpierce/go-forceexport"
 	"github.com/golang/mock/gomock"
@@ -52,6 +54,18 @@ var cipherSuites = []*qtls.CipherSuiteTLS13{
 	},
 }
 
+func splitHexString(s string) (slice []byte) {
+	for _, ss := range strings.Split(s, " ") {
+		if ss[0:2] == "0x" {
+			ss = ss[2:]
+		}
+		d, err := hex.DecodeString(ss)
+		Expect(err).ToNot(HaveOccurred())
+		slice = append(slice, d...)
+	}
+	return
+}
+
 func init() {
 	if err := forceexport.GetFunc(&aeadChaCha20Poly1305, "github.com/marten-seemann/qtls.aeadChaCha20Poly1305"); err != nil {
 		panic(err)