Model:

class Post(models.Model):
    title = models.CharField(max_length=255)
    machine_name = models.SlugField(max_length=255, unique=True)
    description = models.CharField(max_length=255, blank=True)
    content = models.TextField(blank=True)
    publication_date = models.DateTimeField()
    published = models.BooleanField(default=True)
    owner = models.ForeignKey(auth.models.User)
    tags=TaggableManager(blank=True)
    keywords = models.CharField(max_length=255, blank=True)
    images = models.ManyToManyField(Image, blank=True )

tests.py

"""
This file demonstrates writing tests using the unittest module. These will pass
when you run "manage.py test".

Replace this with more appropriate tests for your application.
"""

from django.test import TestCase
from posts.models import Post, Image
from django.utils import timezone
from django.contrib.auth.models import User

class PostsTest(TestCase):

    def setUp(self):

        self.user = User.objects.create_user(username='testuser', email='testuser@test.com', password='top_secret')


    def create_image(self, name = 'test_image', image = 'test.jpg'):
        return Image.objects.create(name = name, image = image)

    # Tag list is using django-taggit, in the admin adding tag text separated by a comma adds the tags
    def create_post(self):

        return Post.objects.create(title = 'title',
                                    machine_name = 'machine_name',
                                    description = 'description',
                                    content = 'content',
                                    publication_date = timezone.now(),
                                    owner = self.user,
                                    keywords = 'key')


    def test_image_creation(self):
        i = self.create_image('testImage', 'test.jpg')
        self.assertTrue(isinstance(i, Image))
        self.assertEqual(i.__unicode__(), i.name)


    def test_post_creation(self):
        a = self.create_post()
        self.assertTrue(isinstance(a, Post))
        self.assertEqual(a.__unicode__(), a.title)


    def tearDown(self):
        self.user.delete()