fix leaky state in tests

Author: KoolADE85

tests/integration/mcp/conftest.py

@@ -5,6 +5,8 @@
 import pytest
 import requests
 
+from dash import _get_app
+
 collect_ignore_glob = []
 if sys.version_info < (3, 10):
     collect_ignore_glob.append("*")
@@ -16,6 +18,17 @@ def _enable_mcp_for_integration_tests(monkeypatch):
     monkeypatch.setenv("DASH_MCP_ENABLED", "true")
 
 
+@pytest.fixture(autouse=True)
+def _reset_dash_app_state():
+    """Reset Dash module-level state after each MCP test.
+
+    TODO: this can be removed when 4.2 backend work lands
+    """
+    yield
+    _get_app.APP = None
+    _get_app.app_context.set(None)
+
+
 def _mcp_post(server_url, method, params=None, request_id=1):
     return requests.post(
         f"{server_url}/_mcp",