@Test public void tag_scopedSpan() {

  when(parseValue.apply(input, context)).thenReturn("value");
  tag.tag(input, scopedSpan);
  verify(scopedSpan).isNoop();
  verify(scopedSpan).context();
  verify(parseValue).apply(input, context);
  verifyNoMoreInteractions(parseValue); // doesn't parse twice
  verify(scopedSpan).tag("key", "value");
  verifyNoMoreInteractions(scopedSpan); // doesn't tag twice
}