Added unittests for caching of file links.

Also converted test_auth.py to use the new AbstractPillarTest class.
This class ensures that we test against the testing database, which
is dropped at every setUp()/tearDown().

tests/test_file_caching.py

@@ -0,0 +1,58 @@
+"""Test cases for the /files/{id} entrypoint, testing cache behaviour."""
+
+import bson.tz_util
+import datetime
+from eve import RFC1123_DATE_FORMAT
+
+from common_test_stuff import AbstractPillarTest
+
+
+class FileCachingTest(AbstractPillarTest):
+
+    def test_nonexistant_file(self):
+        with self.app.test_request_context():
+            resp = self.client.get('/files/12345')
+        self.assertEqual(404, resp.status_code)
+
+    def test_existing_file(self):
+        file_id, _ = self._ensure_file_exists()
+
+        resp = self.client.get('/files/%s' % file_id)
+        self.assertEqual(200, resp.status_code)
+
+    def test_if_modified_304(self):
+        with self.app.test_request_context():
+            # Make sure the file link has not expired.
+            expires = datetime.datetime.now(tz=bson.tz_util.utc) + datetime.timedelta(minutes=1)
+            file_id, file_doc = self._ensure_file_exists(file_overrides={
+                u'link_expires': expires
+            })
+
+            updated = file_doc['_updated'].strftime(RFC1123_DATE_FORMAT)
+            resp = self.client.get('/files/%s' % file_id,
+                                   headers={'if_modified_since': updated})
+        self.assertEqual(304, resp.status_code)
+
+    def test_if_modified_200(self):
+        file_id, file_doc = self._ensure_file_exists()
+
+        delta = datetime.timedelta(days=-1)
+
+        with self.app.test_request_context():
+            updated = (file_doc['_updated'] + delta).strftime(RFC1123_DATE_FORMAT)
+            resp = self.client.get('/files/%s' % file_id,
+                                   headers={'if_modified_since': updated})
+        self.assertEqual(200, resp.status_code)
+
+    def test_if_modified_link_expired(self):
+        with self.app.test_request_context():
+            # Make sure the file link has expired.
+            expires = datetime.datetime.now(tz=bson.tz_util.utc) - datetime.timedelta(seconds=1)
+            file_id, file_doc = self._ensure_file_exists(file_overrides={
+                u'link_expires': expires
+            })
+
+            updated = file_doc['_updated'].strftime(RFC1123_DATE_FORMAT)
+            resp = self.client.get('/files/%s' % file_id,
+                                   headers={'if_modified_since': updated})
+        self.assertEqual(200, resp.status_code)