/**
  * @param ActivityUsage $usage
  */
 public function add(ActivityUsage $usage)
 {
     $date = $usage->getDate();
     $key = $date->format('Y-m-d');
     if (empty($this->subjectCollections[$key])) {
         $this->subjectCollections[$key] = new ActivitySubjectCollection();
     }
     $this->subjectCollections[$key]->add($usage);
 }
 public function testGetDate()
 {
     $this->assertEquals($this->date, $this->activityUsage->getDate());
 }