Create a mechanism for marking tests "logcontext clean" (#8399)

tests/crypto/test_keyring.py

@@ -41,6 +41,7 @@ from synapse.storage.keys import FetchKeyResult
 
 from tests import unittest
 from tests.test_utils import make_awaitable
+from tests.unittest import logcontext_clean
 
 
 class MockPerspectiveServer:
@@ -67,6 +68,7 @@ class MockPerspectiveServer:
         signedjson.sign.sign_json(res, self.server_name, self.key)
 
 
+@logcontext_clean
 class KeyringTestCase(unittest.HomeserverTestCase):
     def check_context(self, val, expected):
         self.assertEquals(getattr(current_context(), "request", None), expected)
@@ -309,6 +311,7 @@ class KeyringTestCase(unittest.HomeserverTestCase):
         mock_fetcher2.get_keys.assert_called_once()
 
 
+@logcontext_clean
 class ServerKeyFetcherTestCase(unittest.HomeserverTestCase):
     def make_homeserver(self, reactor, clock):
         self.http_client = Mock()

tests/unittest.py

@@ -23,7 +23,7 @@ import logging
 import time
 from typing import Optional, Tuple, Type, TypeVar, Union
 
-from mock import Mock
+from mock import Mock, patch
 
 from canonicaljson import json
 
@@ -169,6 +169,19 @@ def INFO(target):
     return target
 
 
+def logcontext_clean(target):
+    """A decorator which marks the TestCase or method as 'logcontext_clean'
+
+    ... ie, any logcontext errors should cause a test failure
+    """
+
+    def logcontext_error(msg):
+        raise AssertionError("logcontext error: %s" % (msg))
+
+    patcher = patch("synapse.logging.context.logcontext_error", new=logcontext_error)
+    return patcher(target)
+
+
 class HomeserverTestCase(TestCase):
     """
     A base TestCase that reduces boilerplate for HomeServer-using test cases.