public function __construct(AfterBackgroundTested $event, $steps)
 {
     $this->event = $event;
     $num_steps = count($event->getBackground()->getSteps());
     $this->steps = array_slice($steps, -$num_steps);
 }
 public function afterBackground(AfterBackgroundTested $event)
 {
     $this->background = new Background($event, $this->steps);
     $background_steps = count($event->getBackground()->getSteps());
     $this->steps = array_slice($this->steps, 0, count($this->steps) - $background_steps);
 }