test: use public API for streaming structured output

Agent-Logs-Url: https://github.com/microsoft/agent-framework/sessions/f62076ef-558d-49e8-8fe2-f38d527c9639

Co-authored-by: eavanvalkenburg <13749212+eavanvalkenburg@users.noreply.github.com>

python/packages/openai/agent_framework_openai/_chat_client.py

@@ -619,6 +619,9 @@ class RawOpenAIChatClient(  # type: ignore[misc]
             response_format: Any | None = None
 
             def _finalize_with_captured_format(updates: Sequence[ChatResponseUpdate]) -> ChatResponse[Any]:
+                # ResponseStream only calls the finalizer after iterating or draining `_stream()`,
+                # so `response_format` has already been populated from the validated request state
+                # unless request setup failed before streaming began.
                 return self._finalize_response_updates(updates, response_format=response_format)
 
             async def _stream() -> AsyncIterable[ChatResponseUpdate]:

python/packages/openai/tests/openai/test_openai_chat_client.py

@@ -874,7 +874,11 @@ async def test_streaming_text_format_preserves_final_structured_output() -> None
         patch.object(client.client.responses, "stream", return_value=fake_stream_ctx),
         patch.object(client, "_get_metadata_from_response", return_value={}),
     ):
-        stream = client._inner_get_response(messages=[Message(role="user", contents=["Hi"])], options={}, stream=True)
+        stream = client.get_response(
+            messages=[Message(role="user", contents=["Hi"])],
+            options={"response_format": OutputStruct},
+            stream=True,
+        )
         response = await stream.get_final_response()
 
     assert response.model == "test-model"