public function sum_number_some()
{
$xs = $this->createHotObservable([onNext(150, 1), onNext(210, 2), onNext(220, 3), onNext(230, 4), onCompleted(250)]);
$results = $this->scheduler->startWithCreate(function () use($xs) {
return $xs->sum();
});
$this->assertMessages([onNext(250, 2 + 3 + 4), onCompleted(250)], $results->getMessages());
}