public static Builder newIntegerColumnDefBuilder() {
    return new Builder();
  }
@Test
  public void builder_build_throws_NPE_if_no_name_was_set() {
    IntegerColumnDef.Builder builder = newIntegerColumnDefBuilder();

    assertThatThrownBy(builder::build)
      .isInstanceOf(NullPointerException.class)
      .hasMessage("Column name cannot be null");
  }