public void handleReceive(RpcClientResponse response, Span span) {
    handleFinish(response, span);
  }
@Test void handleReceive_responseRequired() {
    brave.Span span = mock(brave.Span.class);

    assertThatThrownBy(() -> handler.handleReceive(null, span))
        .isInstanceOf(NullPointerException.class)
        .hasMessage("response == null");
  }