if (!status.ok())
    GTEST_SKIP() << "NewWritableFile() not supported: " << status;

  int64_t position;
  status = file->Tell(&position);
  EXPECT_PRED2(UnimplementedOrReturnsCode, status, Code::OK);
  if (!status.ok()) GTEST_SKIP() << "Tell() not supported: " << status;
  EXPECT_EQ(position, 0);

  const std::string test_data("asdf");
  status = file->Append(test_data);

                 TF_Status* status);

  /// Returns the current write position in `*file`.
  ///
  /// Plugins should ensure that the implementation is idempotent, 2 identical
  /// calls result in the same answer.
  ///
  /// Plugins:
  ///   * Must set `status` to `TF_OK` and return current position if no error.
  ///   * Must set `status` to any other value and return -1 in case of error.