title: django test : accessing database from a form returns empty list
body: <p>I'm using a Django form, containing a ChoiceField list. This list content is retrieved from the form, using orm. 
  It works in the application, but in the test, the utility method returns an empty content.
  Before I create the form, I'm querying the same table as the utility method, and it returns 3 records.
  Any idea why the utility method considers the table empty ?</p>
  
  <h1>1) the form :</h1>
  
  <pre><code>class JournalForm(forms.Form):
      journal_id = forms.CharField(widget=forms.HiddenInput(), required=False)
      journal_name = forms.CharField(label=ugettext('Journal name'), max_length=100, required=False)
      list_field = list()
      list_field.append(('0',ugettext('select')))
      list_field = list_field + getFieldOfInterestList()
      journal_fieldOfInterest = forms.ChoiceField(initial='0', choices = list_field, label=ugettext('Field of interest'), widget=forms.Select(), required=False)
  </code></pre>
  
  <h1>2) the utility method :</h1>
  
  <pre><code>def getFieldOfInterestList():
      try:
          interest_list = list()
          for field in FieldOfInterest.objects.all().order_by('name'):
              interest_list.append((str(field.id_field),field.name))
          return interest_list     
      except Exception as ex:
          print("an error in getFieldOfInterestList() : " + str(ex))
          return list()
  </code></pre>
  
  <h1>3) the test :</h1>
  
  <pre><code>@pytest.mark.django_db
  def testJournals(self):
    # this query returns 3 fields, previously added in this test (so test database is not empty)
    print("nb fields = " + str(FieldOfInterest.objects.all().count()))
    journalForm = JournalForm(
            initial={
                  'journal_name': 'Aquatic Botany',
                  'journal_fieldOfInterest': 3,
    })  
    print("form = " + str(journalForm))
    # returns False
    print("is valid = " + str(journalForm.is_valid()))
  </code></pre>
  
  <p>Printed form should have more options in the select, but only contains the default one :</p>
  
  <pre><code>&lt;tr&gt;&lt;th&gt;&lt;label for="id_journal_name"&gt;Journal name:&lt;/label&gt;&lt;/th&gt;&lt;td&gt;&lt;input id="id_journal_name" maxlength="100" name="journal_name" type="text" value="Aquatic Botany" /&gt;&lt;/td&gt;&lt;/tr&gt;
  &lt;tr&gt;&lt;th&gt;&lt;label for="id_journal_fieldOfInterest"&gt;Field of interest:&lt;/label&gt;&lt;/th&gt;&lt;td&gt;&lt;select id="id_journal_fieldOfInterest" name="journal_fieldOfInterest"&gt;
  &lt;option value="0"&gt;select&lt;/option&gt;
  &lt;/select&gt;&lt;/td&gt;&lt;/tr&gt;
  </code></pre>
  
  <p>Thank you for reading me.</p>