@Test
public void pastWeatherToObservable() throws IOException {

    CompletableFuture<Stream<WeatherInfo>> infos = new WeatherWebApi()
        .pastWeather(37.017, -7.933, parse("2019-02-01"), parse("2019-03-28"));
    Observable<WeatherInfo> wis = Observable
        .fromFuture(infos)
        .flatMap(strm -> fromIterable(strm::iterator));
    WeatherInfo wi = wis.firstElement().blockingGet();
    assertEquals(parse("2019-02-01"), wi.getDate());
    assertEquals(14, wi.getTempC());
    assertEquals(13.8, wi.getPrecipMM());
    assertEquals("Patchy rain possible", wi.getDesc());
}