django test file download - "ValueError: I/O operation on closed file"

Question

I have code for a view which serves a file download, and it works fine in the browser. Now I am trying to write a test for it, using the internal django Client.get:

    response = self.client.get("/compile-book/", {'id': book.id})
    self.assertEqual(response.status_code, 200)
    self.assertEquals(response.get('Content-Disposition'), 
                      "attachment; filename=book.zip")

so far so good. Now I would like to test if the downloaded file is the one I expect it to download. So I start by saying:

    f = cStringIO.StringIO(response.content)

Now my test runner responds with:

Traceback (most recent call last):
  File ".../tests.py", line 154, in test_download
    f = cStringIO.StringIO(response.content)
  File "/home/epub/projects/epub-env/lib/python2.7/site-packages/django/http/response.py", line 282, in content
    self._consume_content()
  File "/home/epub/projects/epub-env/lib/python2.7/site-packages/django/http/response.py", line 278, in _consume_content
    self.content = b''.join(self.make_bytes(e) for e in self._container)   
  File "/home/epub/projects/epub-env/lib/python2.7/site-packages/django/http/response.py", line 278, in <genexpr>
    self.content = b''.join(self.make_bytes(e) for e in self._container)   
  File "/usr/lib/python2.7/wsgiref/util.py", line 30, in next 
    data = self.filelike.read(self.blksize) 
ValueError: I/O operation on closed file

Even when I do simply: self.assertIsNotNone(response.content) I get the same ValueError

The only topic on the entire internet (including django docs) I could find about testing downloads was this stackoverflow topic: Django Unit Test for testing a file download. Trying that solution led to these results. It is old and rare enough for me to open a new question.

Anybody knows how the testing of downloads is supposed to be handled in Django? (btw, running django 1.5 on python 2.7)

Answer 1

This works for us. We return rest_framework.response.Response but it should work with regular Django responses, as well.

import io
response = self.client.get(download_url, {'id': archive_id})
downloaded_file = io.BytesIO(b"".join(response.streaming_content))

Note: streaming_content is only available for StreamingHttpResponse (also Django 1.10): https://docs.djangoproject.com/en/1.10/ref/request-response/#django.http.StreamingHttpResponse.streaming_content