public function testSetter()
 {
     $seq = new Sequence([1, 2, 3]);
     $seq[2] = 4;
     $seq->set(3, 5);
     $seq["notCorrectKey"] = 6;
     $seq[] = 7;
     $this->assertEquals([1, 2, 4, 5, 6, 7], $seq->toArray());
 }