Rx\Observable::emptyObservable PHP 메소드

    public static function emptyObservable()
    {
        return new EmptyObservable();
    }

 /**
  * @test
  */
 public function timestamp_empty()
 {
     $results = $this->scheduler->startWithCreate(function () {
         return Observable::emptyObservable($this->scheduler)->timestamp($this->scheduler);
     });
     $this->assertMessages([onCompleted(201)], $results->getMessages());
 }