title: Mocking a Custom File Storage Backend
body: <p>I've created a custom file storage backend that calls out to Amazon S3 using boto and stores the files there (I know django-storages handles this as well, but we ran into several issues with it). I'm storing it in a utils module and using it in my models like this: </p>
  
  <pre><code>from utils.s3 import S3Storage
  
  class Photo(models.Model):
    image = models.ImageField(storage=S3Storage(), upload_to="images")
  </code></pre>
  
  <p>Thus any time a photo is created with an image file, the image file is uploaded to an S3 bucket. </p>
  
  <p>I don't want to make calls out to S3 during my tests, but figuring out exactly what to mock in this situation is difficult. I can't mock out the entire image field, because I need to test creating the model through Tastypie. </p>
  
  <p>Any ideas? </p>