@Test
public void onNext_Error() throws Exception {

  Logger OfframpClientImplLogger = (Logger) LoggerFactory.getLogger(OfframpClientImpl.class);
  ListAppender<ILoggingEvent> listAppender = new ListAppender<>();
  listAppender.start();
  OfframpClientImplLogger.addAppender(listAppender);
  Error error = new Error("That thing was wrong");
  underTest.onNext(error);
  List<ILoggingEvent> logsList = listAppender.list;
  assertThat(logsList.get(0).getMessage(), is("That thing was wrong"));
  assertEquals(Level.ERROR, logsList.get(0).getLevel());
}