"message M1 {\n" +
" required string b = 2;\n" +
"}";
FileDescriptorSource fileDescriptorSource = new FileDescriptorSource();
fileDescriptorSource.addProtoFile("test_proto_path/file1.proto", file1);
fileDescriptorSource.addProtoFile("test_proto_path/file2.proto", file2);
parseAndResolve(fileDescriptorSource);
}