Django : fixtures object not retrievable

I didn't see anywhere that LiveServerTestCase wasn't loading fixtures, but when i execute the following :

class FrontTest(LiveServerTestCase):

    fixtures = ['event.json']


    @classmethod
    def setUpClass(cls):
        super().setUpClass()
        print(Event.objects.all())

The output is :

Using existing test database for alias 'default'...
[]

While when i use TestCase

class FrontTest(TestCase):

    fixtures = ['event.json']


    @classmethod
    def setUpClass(cls):
        super().setUpClass()
        print(Event.objects.all())

The ouput is :

[<Event: event search>]

Do you know why my fixture is loaded only in TestCase ? I'd really like to make it work to use Selenium. Thanks !

PS : event.json :

{
       "model": "mezzanine_agenda.event",
       "pk": 1,
       "fields": {
          "comments_count": 0,
          "keywords_string": "",
          "rating_count": 0,
          "rating_sum": 0,
          "rating_average": 0.0,
          "site": 1,
          "title": "event search",
          "slug": "event-search",
          "_meta_title": "",
          "description": "event search",
          "gen_description": true,
          "created": "2018-05-25T15:49:55.223Z",
          "updated": "2018-05-25T15:49:55.257Z",
          "status": 2,
          "publish_date": "2018-05-25T15:49:32Z",
          "expiry_date": null,
       }
    }, 

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