@Test
public void testTraceHeader() throws Exception {

  SpanContext contextFromHeader = mock(SpanContext.class);
  when(request.getHeader(SpanContextFactory.headerKey())).thenReturn("traceid/spanid");
  when(spanContextFactory.fromHeader("traceid/spanid")).thenReturn(contextFromHeader);
  valve.invoke(request, response);
  verify(spanContextHandler).attach(contextFromHeader);
}