/**
  * @test
  * @expectedException \InvalidArgumentException
  */
 public function throws_an_exception_when_adding_a_skill_whose_name_already_exists_in_the_category()
 {
     $category = new Category();
     $skill = (new Skill())->setTitle('foo');
     $duplicate = (new Skill())->setTitle('foo');
     $category->addSkill($skill);
     $category->addSkill($duplicate);
 }