Rx\Functional\Operator\ConcatMapTest::concatMap_Then_Complete_Task PHP Method

    public function concatMap_Then_Complete_Task()
    {
        $xs = Observable::fromArray([4, 3, 2, 1]);
        $results = [];
        $completed = false;
        $xs->concatMap(function ($x, $i) {
            return Observable::just($x + $i);
        })->subscribeCallback(function ($x) use(&$results) {
            $results[] = $x;
        }, function ($e) {
            $this->fail('Should not get an error');
        }, function () use(&$completed) {
            $completed = true;
        });
        $this->assertTrue($completed);
        $this->assertEquals([4, 4, 4, 4], $results);
    }