client = TestClient(app)


def test_default_response_class_skips_json_dumps():
    """When no response_class is set, the fast path serializes directly to
    JSON bytes via Pydantic's dump_json and never calls json.dumps."""
    with patch(
        "starlette.responses.json.dumps", wraps=__import__("json").dumps
    ) as mock_dumps:
        response = client.get("/default")
    assert response.status_code == 200

        # self._type_adapter.validate_python(value)
        # This uses Pydantic's dump_json() which serializes directly to JSON
        # bytes in one pass (via Rust), avoiding the intermediate Python dict
        # step of dump_python(mode="json") + json.dumps().
        return self._type_adapter.dump_json(
            value,
            include=include,
            exclude=exclude,
            by_alias=by_alias,

    by_alias: bool = True,
    exclude_unset: bool = False,
    exclude_defaults: bool = False,
    exclude_none: bool = False,
    is_coroutine: bool = True,
    endpoint_ctx: EndpointContext | None = None,
    dump_json: bool = False,
) -> Any:
    if field:
        if is_coroutine:
            value, errors = field.validate(response_content, {}, loc=("response",))
        else:
            value, errors = await run_in_threadpool(