Add more test helpers and integration tests for SyncApp's media sync feature using WebTest's TestApp.

Add test helpers for creating, inspecting and manipulating instances of SyncApp and RestApp.
Add subclasses of Anki's RemoteServer and RemoteMediaServer for communicating with the wrapped SyncApp instance under test.
Add helpers for monkey patching Anki's MediaManager and DB for easier testing.
Add test assets directory.

tests/helpers/mock_servers.py

@@ -0,0 +1,68 @@
+# -*- coding: utf-8 -*-
+
+
+import logging
+
+
+from anki.sync import HttpSyncer, RemoteServer, RemoteMediaServer, FullSyncer
+
+
+class MockServerConnection(object):
+    """
+    Mock for HttpSyncer's con attribute, a httplib2 connection. All requests
+    that would normally got to the remote server will be redirected to our
+    server_app_to_test object.
+    """
+
+    def __init__(self, server_app_to_test):
+        self.test_app = server_app_to_test
+
+    def request(self, uri, method='GET', headers=None, body=None):
+        if method == 'POST':
+            logging.debug("Posting to URI '{}'.".format(uri))
+            logging.info("Posting to URI '{}'.".format(uri))
+            test_response = self.test_app.post(uri,
+                                               params=body,
+                                               headers=headers,
+                                               status="*")
+
+            resp = test_response.headers
+            resp.update({
+                "status": str(test_response.status_int)
+            })
+            cont = test_response.body
+            return resp, cont
+        else:
+            raise Exception('Unexpected HttpSyncer.req() behavior.')
+
+
+class MockRemoteServer(RemoteServer):
+    """
+    Mock for RemoteServer. All communication to our remote counterpart is
+    routed to our TestApp object.
+    """
+
+    def __init__(self, hkey, server_test_app):
+        # Create a custom connection object we will use to communicate with our
+        # 'remote' server counterpart.
+        connection = MockServerConnection(server_test_app)
+        HttpSyncer.__init__(self, hkey, connection)
+
+    def syncURL(self):  # Overrides RemoteServer.syncURL().
+        return "/sync/"
+
+
+class MockRemoteMediaServer(RemoteMediaServer):
+    """
+    Mock for RemoteMediaServer. All communication to our remote counterpart is
+    routed to our TestApp object.
+    """
+
+    def __init__(self, col, hkey, server_test_app):
+        # Create a custom connection object we will use to communicate with our
+        # 'remote' server counterpart.
+        connection = MockServerConnection(server_test_app)
+        HttpSyncer.__init__(self, hkey, connection)
+
+    def syncURL(self):  # Overrides RemoteServer.syncURL().
+        return "/msync/"