'IOError: [Errno 2] No such file or directory' when testing file uploads

[Kevin Harvey]

I'm trying to write a test for a FileField on a model Photo. The FieldField is inherited from an base class Asset. I need to save the dimensions of the photo in the database, so I've got my own save method on my Photo model:

def save(self, *args, **kwargs):
    # save the instance, so we can use the uploaded photo
    super(Photo, self).save(*args, **kwargs)
    im = Image.open(os.path.join(MEDIA_ROOT, self.file.name))
    self.width, self.height = im.size
    super(Photo, self).save(*args, **kwargs)

This works, but I can't test it. When I try to create an instance of this model in the test suite, it appears that the file is never moved to the MEDIA_ROOT, and self.file.name refers to the original file in the test directory of my app.

======================================================================
ERROR: testPhoto (caramel.content.tests.modelTests.ContentTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "../myproject/myproject/myapp/tests/modelTests.py", line 22, in setUp
    credit="John Smith")
  File "/Users/username/workspace/eclipse/lib/python2.7/site-packages/django/db/models/manager.py", line 138, in create
    return self.get_query_set().create(**kwargs)
  File "/Users/username/workspace/eclipse/lib/python2.7/site-packages/django/db/models/query.py", line 360, in create
    obj.save(force_insert=True, using=self.db)
  File "../myproject/myproject/myapp/models.py", line 97, in save
    im = Image.open(os.path.join(MEDIA_ROOT, self.file.name))
  File "/Users/username/workspace/eclipse/lib/python2.7/site-packages/PIL/Image.py", line 1952, in open
    fp = __builtin__.open(fp, "rb")
IOError: [Errno 2] No such file or directory: '/Users/username/workspace/eclipse/project/media/../myproject/myproject/myapp/tests/assets/test.jpg'

I'm using PIL's width/height methods here because I can't use Django's own get_image_dimensions, as it's not an ImageField. Thanks in advance.

Kevin