fix: allow test modules in provider namespace validation

Allow test_ prefixed modules (pytest convention) and add
autogen_test_utils to trusted namespaces. Remove conftest-based
env var approach which was unreliable across package boundaries.

Author: victordibia

python/packages/autogen-core/src/autogen_core/_component_config.py

@@ -58,6 +58,7 @@ def _type_to_provider_str(t: type) -> str:
     "autogen_ext.",
     "autogen_studio.",
     "autogenstudio.",
+    "autogen_test_utils.",
 )
 
 
@@ -253,7 +254,10 @@ def load_component(
         module_path, class_name = output
 
         trusted = _get_trusted_namespaces()
-        if not any(module_path.startswith(ns) or module_path == ns.rstrip(".") for ns in trusted):
+        # Also allow test modules (pytest convention) to load components
+        module_name = module_path.rsplit(".", maxsplit=1)[-1]
+        is_test_module = module_name.startswith("test_") or module_path.startswith("test_")
+        if not is_test_module and not any(module_path.startswith(ns) or module_path == ns.rstrip(".") for ns in trusted):
             raise ValueError(
                 f"Provider module '{module_path}' is not in a trusted namespace. "
                 f"Allowed namespaces by default: autogen_core, autogen_agentchat, autogen_ext, "