Duplicate entry mysql error when loading fixtures in symfony2

Question

I started to learn symfony2 after I used symfony 1.4. I use the jobeet tutorial for symfony 2.3. I'm at day 6 where I should add an expired job with fixtures. I'm totally screwed up. I follow every single letter of the tutorial but can't get it work. When running php app/console doctrine:fixtures:load I get the following error `

[PDOException] SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'Programming' for key 'UNIQ_64C19C15E237E06' 

At the comments I don't see any comment about the error I get. There 2 jobs now. A programming category and a design category. When I try to add another job with programming category, it gives me an error. I know what is the error with the query, I just don't understand why it wants to do the query that way. I figured out that the problem is caused by the second job with programming category. I have the LoadCategoryData.php:

class LoadCategoryData extends AbstractFixture implements OrderedFixtureInterface{


public function load(ObjectManager $em){
    $design = new Category();
    $design->setName('Design');
    $programming = new Category();
    $programming->setName('Programming');
    $manager = new Category();
    $manager->setName('Manager');
    $administrator = new Category();
    $administrator->setName('Administrator');
    $em->persist($design);
    $em->persist($programming);
    $em->persist($manager);
    $em->persist($administrator);
    $this->addReference('category-design', $design);
    $this->addReference('category-programming', $programming);
    $this->addReference('category-manager', $manager);
    $this->addReference('category-administrator', $administrator);
  }
  public function getOrder(){
    return 1;
  }
}

And the LoadJobData.php(I will only show the 2 with the programming category):

//...
$job_expired->setCategory($em->merge($this->getReference('category-programming')));
//...
$job_sensio_labs->setCategory($em->merge($this->getReference('category-programming')));
//...
$em->persist($job_expired);
$em->persist($job_sensio_labs);
$em->flush();

My Category.orm.yml looks like this:

Ibw\JobeetBundle\Entity\Category:
type: entity
table: category
id:
    id:
        type: integer
        generator: { strategy: AUTO }
fields:
    name:
        type: string
        length: 255
        unique: true
oneToMany:
    jobs:
        targetEntity: Job
        mappedBy: category
manyToMany:
    affiliates:
        targetEntity: Affiliate
        mappedBy: categories

And the Job.orm.yml where I set the foreign key:

manyToOne:
    category:
        targetEntity: Category
        inversedBy: jobs
        joinColumn:
            name: category_id
            referencedColumnName: id

I could figure out that the error is caused by the line in the LoadJobData.php where I would set the category but I'm too new to symfony2 and can't find any solution for this. Thanks in advance and sorry for the long post.