fix(tests): resolve test isolation issue in http_handler tests

Fix isinstance() checks failing due to module reload in conftest.py.

The conftest.py fixture reloads the litellm module between test modules,
which causes class references imported at module-level to become stale.
When AsyncHTTPHandler is imported at the top of the file and then litellm
is reloaded by the fixture, the isinstance() check fails because the
returned instance is of the NEW AsyncHTTPHandler class while the test
is checking against the OLD class reference.

Solution: Import AsyncHTTPHandler locally within each test function that
uses isinstance() checks. This ensures we get the fresh class reference
after the module reload.

Fixed tests:
- test_session_reuse_integration
- test_get_async_httpx_client_with_shared_session
- test_get_async_httpx_client_without_shared_session

This resolves intermittent CI failures where parallel test execution
triggers the module reload behavior.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

tests/test_litellm/llms/custom_httpx/test_http_handler.py

@@ -358,38 +358,40 @@ async def test_async_handler_with_shared_session():
 @pytest.mark.asyncio
 async def test_get_async_httpx_client_with_shared_session():
     """Test get_async_httpx_client with shared session"""
-    from litellm.llms.custom_httpx.http_handler import get_async_httpx_client
+    from litellm.llms.custom_httpx.http_handler import get_async_httpx_client, AsyncHTTPHandler as AsyncHTTPHandlerReload
     from litellm.types.utils import LlmProviders
-    
+
     # Create a mock shared session
     mock_session = MockClientSession()
-    
+
     # Test with shared session
     client = get_async_httpx_client(
         llm_provider=LlmProviders.ANTHROPIC,
         shared_session=mock_session  # type: ignore
     )
-    
+
     # Verify the client was created successfully
     assert client is not None
-    assert isinstance(client, AsyncHTTPHandler)
+    # Import locally to avoid stale reference after module reload in conftest
+    assert isinstance(client, AsyncHTTPHandlerReload)
 
 
 @pytest.mark.asyncio
 async def test_get_async_httpx_client_without_shared_session():
     """Test get_async_httpx_client without shared session (backward compatibility)"""
-    from litellm.llms.custom_httpx.http_handler import get_async_httpx_client
+    from litellm.llms.custom_httpx.http_handler import get_async_httpx_client, AsyncHTTPHandler as AsyncHTTPHandlerReload
     from litellm.types.utils import LlmProviders
-    
+
     # Test without shared session
     client = get_async_httpx_client(
         llm_provider=LlmProviders.ANTHROPIC,
         shared_session=None
     )
-    
+
     # Verify the client was created successfully
     assert client is not None
-    assert isinstance(client, AsyncHTTPHandler)
+    # Import locally to avoid stale reference after module reload in conftest
+    assert isinstance(client, AsyncHTTPHandlerReload)
 
 
 @pytest.mark.asyncio
@@ -450,31 +452,32 @@ def test_shared_session_parameter_in_completion():
 @pytest.mark.asyncio
 async def test_session_reuse_integration():
     """Integration test for session reuse functionality"""
-    from litellm.llms.custom_httpx.http_handler import get_async_httpx_client
+    from litellm.llms.custom_httpx.http_handler import get_async_httpx_client, AsyncHTTPHandler as AsyncHTTPHandlerReload
     from litellm.types.utils import LlmProviders
-    
+
     # Create a mock session
     mock_session = MockClientSession()
-    
+
     # Create two clients with the same session
     client1 = get_async_httpx_client(
         llm_provider=LlmProviders.ANTHROPIC,
         shared_session=mock_session  # type: ignore
     )
-    
+
     client2 = get_async_httpx_client(
         llm_provider=LlmProviders.OPENAI,
         shared_session=mock_session  # type: ignore
     )
-    
+
     # Both clients should be created successfully
     assert client1 is not None
     assert client2 is not None
-    
+
     # Both should be AsyncHTTPHandler instances
-    assert isinstance(client1, AsyncHTTPHandler)
-    assert isinstance(client2, AsyncHTTPHandler)
-    
+    # Import locally to avoid stale reference after module reload in conftest
+    assert isinstance(client1, AsyncHTTPHandlerReload)
+    assert isinstance(client2, AsyncHTTPHandlerReload)
+
     # Clean up
     await client1.close()
     await client2.close()