new_contents: from django.db import models
  from django.test import TestCase
  from django_fsm import FSMField, transition
  
  
  class WorkflowMixin(object):
      @transition(field='state', source="*", target='draft')
      def draft(self):
          pass
  
      @transition(field='state', source="draft", target='published')
      def publish(self):
          pass
  
  
  class MixinSupportTestModel(WorkflowMixin, models.Model):
      state = FSMField(default="new")
  
  
  class Test(TestCase):
      def test_usecase(self):
          model = MixinSupportTestModel()
  
          model.draft()
          self.assertEqual(model.state, 'draft')
  
          model.publish()
          self.assertEqual(model.state, 'published')
  
subject: Add mixin support testcase. Close #75