Compatibility test for old Secure Session API

All these dynamic checks in session.New() warrant a test which verifies
that we actually can handle the old interface values and reject invalid
ones.

This test can be removed together with the old SessionCallbacks API.

gothemis/session/session_test.go

@@ -30,6 +30,25 @@ func (clb *testCallbacks) StateChanged(ss *SecureSession, state int) {
 
 }
 
+// TODO: remove together with deprecated SessionCallbacks interface
+type testCallbacksOld struct {
+	a *keys.Keypair
+	b *keys.Keypair
+}
+
+func (clb *testCallbacksOld) GetPublicKeyForId(ss *SecureSession, id []byte) *keys.PublicKey {
+	if bytes.Equal(clientID, id) {
+		return clb.a.Public
+	} else if bytes.Equal(serverID, id) {
+		return clb.b.Public
+	}
+	return nil
+}
+
+func (clb *testCallbacksOld) StateChanged(ss *SecureSession, state int) {
+
+}
+
 func genRandData() ([]byte, error) {
 	dataLength, err := rand.Int(rand.Reader, big.NewInt(2048))
 	if nil != err {
@@ -162,21 +181,8 @@ func serverService(server *SecureSession, ch chan []byte, finCh chan int, t *tes
 	}
 }
 
-func testSession(keytype int, t *testing.T) {
-	kpa, err := keys.New(keytype)
-	if nil != err {
-		t.Error(err)
-		return
-	}
-
-	kpb, err := keys.New(keytype)
-	if nil != err {
-		t.Error(err)
-		return
-	}
-
-	clb := &testCallbacks{kpa, kpb}
-
+func testSession(kpa *keys.Keypair, kpb *keys.Keypair, clb interface{}, t *testing.T) {
+	var err error
 	emptyKey := keys.PrivateKey{Value: []byte{}}
 
 	_, err = New(clientID, nil, clb)
@@ -224,5 +230,53 @@ func testSession(keytype int, t *testing.T) {
 }
 
 func TestSession(t *testing.T) {
-	testSession(keys.TypeEC, t)
+	kpa, err := keys.New(keys.TypeEC)
+	if nil != err {
+		t.Error(err)
+		return
+	}
+
+	kpb, err := keys.New(keys.TypeEC)
+	if nil != err {
+		t.Error(err)
+		return
+	}
+
+	clb := &testCallbacks{kpa, kpb}
+
+	testSession(kpa, kpb, clb, t)
+}
+
+// TODO: remove together with deprecated SessionCallbacks interface
+func TestSessionOldAPI(t *testing.T) {
+	kpa, err := keys.New(keys.TypeEC)
+	if nil != err {
+		t.Error(err)
+		return
+	}
+
+	kpb, err := keys.New(keys.TypeEC)
+	if nil != err {
+		t.Error(err)
+		return
+	}
+
+	clb := &testCallbacksOld{kpa, kpb}
+
+	testSession(kpa, kpb, clb, t)
+}
+
+// TODO: remove together with deprecated SessionCallbacks interface
+func TestSessionInvalidCallbacks(t *testing.T) {
+	keyPair, err := keys.New(keys.TypeEC)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	_, err = New(serverID, keyPair.Private, "definitely not a callback")
+	if err == nil {
+		t.Error("Expected secure.New() to fail for invalid type")
+		return
+	}
 }