diff --git a/zerver/lib/test_classes.py b/zerver/lib/test_classes.py
index c8e02b2a72..78ebf38132 100644
--- a/zerver/lib/test_classes.py
+++ b/zerver/lib/test_classes.py
@@ -73,12 +73,6 @@ import urllib
 import shutil
 import tempfile
 
-API_KEYS = {}  # type: Dict[str, str]
-
-def flush_caches_for_testing() -> None:
-    global API_KEYS
-    API_KEYS = {}
-
 class UploadSerializeMixin(SerializeMixin):
     """
     We cannot use override_settings to change upload directory because
@@ -101,6 +95,10 @@ class ZulipTestCase(TestCase):
     # Ensure that the test system just shows us diffs
     maxDiff = None  # type: Optional[int]
 
+    def setUp(self) -> None:
+        super().setUp()
+        self.API_KEYS = {}  # type: Dict[str, str]
+
     def tearDown(self) -> None:
         super().tearDown()
         # Important: we need to clear event queues to avoid leaking data to future tests.
@@ -409,15 +407,15 @@ class ZulipTestCase(TestCase):
         """
         identifier: Can be an email or a remote server uuid.
         """
-        if identifier in API_KEYS:
-            api_key = API_KEYS[identifier]
+        if identifier in self.API_KEYS:
+            api_key = self.API_KEYS[identifier]
         else:
             if is_remote_server(identifier):
                 api_key = get_remote_server_by_uuid(identifier).api_key
             else:
                 user = get_user(identifier, get_realm(realm))
                 api_key = get_api_key(user)
-            API_KEYS[identifier] = api_key
+            self.API_KEYS[identifier] = api_key
 
         credentials = "%s:%s" % (identifier, api_key)
         return 'Basic ' + base64.b64encode(credentials.encode('utf-8')).decode('utf-8')
diff --git a/zerver/lib/test_runner.py b/zerver/lib/test_runner.py
index 2874da3471..f8e13c9001 100644
--- a/zerver/lib/test_runner.py
+++ b/zerver/lib/test_runner.py
@@ -14,10 +14,9 @@ from django.test import runner as django_runner
 from django.test.runner import DiscoverRunner
 from django.test.signals import template_rendered
 
-from zerver.lib import test_classes, test_helpers
+from zerver.lib import test_helpers
 from zerver.lib.cache import bounce_key_prefix_for_testing
 from zerver.lib.rate_limiter import bounce_redis_key_prefix_for_testing
-from zerver.lib.test_classes import flush_caches_for_testing
 from zerver.lib.sqlalchemy_utils import get_sqlalchemy_connection
 from zerver.lib.test_helpers import (
     write_instrumentation_reports,
@@ -122,8 +121,6 @@ def run_test(test: TestCase, result: TestResult) -> bool:
     bounce_key_prefix_for_testing(test_name)
     bounce_redis_key_prefix_for_testing(test_name)
 
-    flush_caches_for_testing()
-
     if not hasattr(test, "_pre_setup"):
         msg = "Test doesn't have _pre_setup; something is wrong."
         error_pre_setup = (Exception, Exception(msg), None)
@@ -295,8 +292,6 @@ def init_worker(counter: Synchronized) -> None:
     You can now use _worker_id.
     """
 
-    test_classes.API_KEYS = {}
-
     # Clear the cache
     from zerver.lib.cache import get_cache_backend
     cache = get_cache_backend(None)
diff --git a/zerver/tests/test_push_notifications.py b/zerver/tests/test_push_notifications.py
index a0520e487e..c6eacc1c25 100644
--- a/zerver/tests/test_push_notifications.py
+++ b/zerver/tests/test_push_notifications.py
@@ -187,15 +187,14 @@ class PushBouncerNotificationTest(BouncerTestCase):
 
         # We do a bit of hackery here to the API_KEYS cache just to
         # make the code simple for sending an incorrect API key.
-        from zerver.lib.test_classes import API_KEYS
-        API_KEYS[self.server_uuid] = 'invalid'
+        self.API_KEYS[self.server_uuid] = 'invalid'
         result = self.api_post(self.server_uuid, endpoint, {'user_id': user_id,
                                                             'token_kind': token_kind,
                                                             'token': token})
         self.assert_json_error(result, "Zulip server auth failure: key does not match role 1234-abcd",
                                status_code=401)
 
-        del API_KEYS[self.server_uuid]
+        del self.API_KEYS[self.server_uuid]
 
         credentials = "%s:%s" % ("5678-efgh", 'invalid')
         api_auth = 'Basic ' + base64.b64encode(credentials.encode('utf-8')).decode('utf-8')