diff --git a/httpcore/backends/mock.py b/httpcore/backends/mock.py
index 871a2521d..edb613aef 100644
--- a/httpcore/backends/mock.py
+++ b/httpcore/backends/mock.py
@@ -6,8 +6,9 @@
 import anyio
 
 from httpcore import ReadTimeout
-from .base import AsyncNetworkBackend, AsyncNetworkStream, NetworkBackend, NetworkStream
+
 from .._exceptions import ReadError
+from .base import AsyncNetworkBackend, AsyncNetworkStream, NetworkBackend, NetworkStream
 
 
 class MockSSLObject:
diff --git a/tests/_async/test_connection_pool.py b/tests/_async/test_connection_pool.py
index 6c45b020a..812b067dd 100644
--- a/tests/_async/test_connection_pool.py
+++ b/tests/_async/test_connection_pool.py
@@ -8,12 +8,12 @@
     AsyncConnectionPool,
     ConnectError,
     PoolTimeout,
-    ReadTimeout,
     ReadError,
+    ReadTimeout,
     UnsupportedProtocol,
 )
 from httpcore.backends.base import AsyncNetworkStream
-from httpcore.backends.mock import AsyncMockBackend, AsyncHangingStream
+from httpcore.backends.mock import AsyncHangingStream, AsyncMockBackend
 
 
 @pytest.mark.anyio
diff --git a/tests/_sync/test_connection_pool.py b/tests/_sync/test_connection_pool.py
index 1384bef06..b08c10ba6 100644
--- a/tests/_sync/test_connection_pool.py
+++ b/tests/_sync/test_connection_pool.py
@@ -5,15 +5,15 @@
 import pytest
 
 from httpcore import (
-    ConnectionPool,
     ConnectError,
+    ConnectionPool,
     PoolTimeout,
-    ReadTimeout,
     ReadError,
+    ReadTimeout,
     UnsupportedProtocol,
 )
 from httpcore.backends.base import NetworkStream
-from httpcore.backends.mock import MockBackend, HangingStream
+from httpcore.backends.mock import HangingStream, MockBackend
 from tests import concurrency