The capture_items fixture assumes all metrics, logs, and spans have an attributes key, but spans may not have this key. In _span_batcher.py, the attributes key is only added conditionally when item._attributes is truthy. When a span without attributes is captured, accessing json["attributes"].items() will raise a KeyError.

The capture_items fixture unconditionally accesses json["attributes"] (line 353), but _span_batcher._to_transport_format only includes the attributes key when item._attributes is truthy (line 116-119 in _span_batcher.py). While in practice StreamedSpan.end() always sets segment attributes, this creates a fragile dependency on implementation details. If a span somehow ends up without attributes (e.g., through mocking or future code changes), the fixture will raise a KeyError.