More extensive testing in extensions_test.go.

proto/extensions_test.go

@@ -92,3 +92,46 @@ func TestGetExtensionStability(t *testing.T) {
 		t.Errorf("GetExtension() not stable after unmarshaling")
 	}
 }
+
+func TestExtensionsRoundTrip(t *testing.T) {
+	msg := &pb.MyMessage{}
+	ext1 := &pb.Ext{
+		Data: proto.String("hi"),
+	}
+	ext2 := &pb.Ext{
+		Data: proto.String("there"),
+	}
+	exists := proto.HasExtension(msg, pb.E_Ext_More)
+	if exists {
+		t.Error("Extension More present unexpectedly")
+	}
+	if err := proto.SetExtension(msg, pb.E_Ext_More, ext1); err != nil {
+		t.Error(err)
+	}
+	if err := proto.SetExtension(msg, pb.E_Ext_More, ext2); err != nil {
+		t.Error(err)
+	}
+	e, err := proto.GetExtension(msg, pb.E_Ext_More)
+	if err != nil {
+		t.Error(err)
+	}
+	x, ok := e.(*pb.Ext)
+	if !ok {
+		t.Errorf("e has type %T, expected testdata.Ext", e)
+	} else if *x.Data != "there" {
+		t.Errorf("SetExtension failed to overwrite, got %+v, not 'there'", x)
+	}
+	proto.ClearExtension(msg, pb.E_Ext_More)
+	if _, err = proto.GetExtension(msg, pb.E_Ext_More); err != proto.ErrMissingExtension {
+		t.Errorf("got %v, expected ErrMissingExtension", e)
+	}
+	if _, err := proto.GetExtension(msg, pb.E_X215); err == nil {
+		t.Error("expected bad extension error, got nil")
+	}
+	if err := proto.SetExtension(msg, pb.E_X215, 12); err == nil {
+		t.Error("expected extension err")
+	}
+	if err := proto.SetExtension(msg, pb.E_Ext_More, 12); err == nil {
+		t.Error("expected some sort of type mismatch error, got nil")
+	}
+}