title: Django test data persisting across multiple tests despite being TestCase
body: <p>I have a a test case that uses <code>setUp</code> and looks like this:</p>
  
  <pre><code>from django.test import TestCase, Client, TransactionTestCase
  ...
  class TestPancakeView(TestCase):
  
      def setUp(self):
          self.client = Client()
  
          # The Year objects are empty (none here - expected)
          print(Year.objects.all())
  
          # When I run these Test by itself, these are empty (expected)
          # When I run the whole file, this prints out a number of
          # Pancake objects causing these tests to fail - these objects appear
          # to be persisting from previous tests
          print(Pancake.objects.all())
  
          # This sets up my mock/test data
          data_setup.basic_setup(self)
  
          # This now prints out the expected years that data_setup creates
          print(Year.objects.all())
  
          # This prints all the objects that I should have 
          # But if the whole file is ran - it's printing objects
          # That were created in other tests
          print(Pancake.objects.all())
  
          [...tests and such...]
  </code></pre>
  
  <p><code>data_setup.py</code> is a file that just creates all the appropriate test-data for my tests when it needs them. I'm using Factory Boy for creating test data.</p>
  
  <p>When I run <code>TestPancakeView</code> by itself - my tests pass as expected.</p>
  
  <p>When I run my entire <code>test_views.py</code> file, my <code>TestPancakeView</code> tests fail.</p>
  
  <p>If I change it to TransactionTestCase - it still fails when I run the whole file.</p>
  
  <p>I'm creating the Pancake test data like this:</p>
  
  <pre><code>        f.PancakeFactory.create_batch(
              2,
              flavor=blueberry,
              intensity='high'
          )
  </code></pre>
  
  <p>No other tests exhibit this behavior, they all act the same way when I run them individually or when I run them as part of the entire file.</p>