@Override
  public MergeAppend appendFile(DataFile file) {
    add(file);
    return this;
  }
@TestTemplate
  public void appendNullFile() {
    assertThatThrownBy(() -> table.newAppend().appendFile(null).commit())
        .isInstanceOf(NullPointerException.class)
        .hasMessage("Invalid data file: null");
  }