/**
  * {@inheritdoc}
  */
 public function has($service)
 {
     $this->assertServiceHaveType($service);
     return $this->services->contains($service);
 }
 public function testCanTestForExistenceOfItemInQueue()
 {
     $this->assertTrue($this->queue->contains('foo'));
     $this->assertFalse($this->queue->contains('foobar'));
 }