@Test
public void shouldRespondToObservationRequest_exception() {

    Callback<CoapPacket> respCallback = mock(Callback.class);
    server.observe("/test", LOCAL_5683, respCallback, "aa".getBytes(), TransportContext.NULL);
    verifyMakeRequest_andThen().callException(new IOException());
    verify(respCallback).callException(isA(IOException.class));
}