@Override
  public MetricsContext.Unit unit() {
    return unit;
  }
@Test
  public void noop() {
    assertThat(DefaultCounter.NOOP.unit()).isEqualTo(Unit.UNDEFINED);
    assertThat(DefaultCounter.NOOP.isNoop()).isTrue();
    assertThatThrownBy(DefaultCounter.NOOP::value)
        .isInstanceOf(UnsupportedOperationException.class)
        .hasMessage("NOOP counter has no value");
  }