TF_WritableFileHandle* handle;
    TF_NewWritableFile(filepath.c_str(), &handle, s);
    ASSERT_TF_OK(s) << "NewWritableFile failed for " << filepath << ": "
                    << TF_Message(s);

    const char* data = "Hello, world!\n";
    TF_AppendWritableFile(handle, data, strlen(data), s);
    ASSERT_TF_OK(s) << "TF_AppendWritableFile failed to append data to file at "
                    << filepath << ": " << TF_Message(s);