Rx\React\Promise::rejected PHP Method

    public static function rejected($exception)
    {
        $d = new Deferred();
        $d->reject($exception);
        return $d->promise();
    }

 /**
  * @test
  *
  */
 public function from_promise_failure()
 {
     $p = Promise::rejected(new Exception('error'));
     $source = Promise::toObservable($p);
     $source->subscribe(new CallbackObserver(function ($x) {
         $this->assertFalse(true);
     }, function ($error) {
         $this->assertEquals($error, new Exception('error'));
     }, function () {
         $this->assertFalse(true);
     }));
 }