fix(storage): support updated GapicCallable metadata in tests

[shuoweil]

In google-api-core>=2.34.0 (PR #17616), _GapicCallable replaced the internal _metadata attribute with _default_metadata / _x_goog_api_client.

This PR updates test_init_default_client_info in packages/google-cloud-bigquery-storage/tests/unit/test_read_client_v1.py to check _default_metadata with a fallback to _metadata, maintaining compatibility across both older and newer google-api-core releases.

Fixes #<543999765> 🦕

[gemini-code-assist]

Code Review

This pull request updates the unit test test_init_default_client_info in test_read_client_v1.py to safely retrieve metadata from wrapped methods by checking _default_metadata before falling back to _metadata. This ensures the test is more resilient to changes in how metadata is stored on wrapped methods. There are no review comments, and I have no additional feedback to provide.

[daniel-sanche]

Can you try to write this test in a way that doesn't depend on internal attributes? That would make it more resilient to these kinds of failures in the future

One option is to mock wrap_method:

@pytest.mark.parametrize(
    "module_under_test",
    ["google.cloud.bigquery_storage_v1", "google.cloud.bigquery_storage_v1beta2"],
)
def test_init_default_client_info(module_under_test):
    mut = importlib.import_module(module_under_test)
    creds = mock.Mock(spec=credentials.Credentials)
    expected_client_info = f"gccl/{mut.__version__}"

    with mock.patch("google.api_core.gapic_v1.method.wrap_method") as mock_wrap:
        mut.BigQueryWriteClient(credentials=creds)

        assert mock_wrap.call_count > 0 # <- maybe set the expected number here? Or something more robust?
        for call in mock_wrap.call_args_list:
            client_info = call.kwargs.get("client_info")
            assert client_info is not None
            assert expected_client_info in client_info.to_user_agent()

[shuoweil]

Thanks @daniel-sanche for the suggestion! Done.

[daniel-sanche]

LGTM