@Test
public void keepHeaderUnchangedIfContextAbsent() {

  when(invocation.getAttachment(OmegaContext.GLOBAL_TX_ID_KEY)).thenReturn(null);
  when(invocation.getAttachment(OmegaContext.LOCAL_TX_ID_KEY)).thenReturn(null);
  filter.invoke(null, invocation);
  assertThat(invocation.getAttachments().isEmpty(), is(true));
}