fix: validate response shape before indexing in test_query_load_exten...

[BigNounce90]

Summary

test_query_load_extension called json.loads(result.output)[0] without first checking that the parsed list is non-empty, so any empty or truncated CLI output would raise an IndexError instead of a meaningful assertion failure. The fix extracts the parsed result into a local variable and asserts its length before indexing.

Why it matters

If the CLI silently produces no rows (e.g. due to a regression in the output serialiser or an unexpected empty result set), the test crashes with an opaque IndexError rather than failing with a diagnostic message pointing at the actual assertion.

Testing

The new assert len(rows) == 1 line fires before the index access; all previously-passing inputs still reach and satisfy the original key-shape assertion unchanged.

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📚 Documentation preview 📚: https://sqlite-utils--743.org.readthedocs.build/en/743/