docs(mutmut): document why the mutation gate covers only retry.py#107
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The [tool.mutmut] policy declares 7 security-critical serving modules as mutation targets (enforced by test_mutmut_policy.py), but the CI gate (scripts/mutation_report.py) mutates only the duckdb-free retry.py. Those serving modules transitively import duckdb, whose compiled subpackage (_duckdb._sqltypes) fails to import inside mutmut's mutants/ workspace and crashes the run with every mutant left "not checked" -- reproduced in a Linux container, so it is a mutmut x duckdb harness limitation, not platform-specific. Make this gap explicit at the three places a reader meets it (the pyproject policy list, the runner's MODULE_TARGETS, and the policy test) so declared coverage is not mistaken for live mutation coverage. Comments only; no logic change. Extending the gate to serving modules needs isolated mutant execution (subprocess/spawn) or a different mutation tool. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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What
Document why the mutation-testing gate only mutates
sdk/agentflow/retry.py, despite[tool.mutmut]declaring 7 security-critical serving modules as targets.Why
tests/unit/test_mutmut_policy.pyenforces that 7 security-critical modules (sql_guard, authmanager/key_rotation,masking,rate_limiter,nl_queries,sql_builder) are declared mutation targets. But the CI gate (scripts/mutation_report.py) drives mutation from its ownMODULE_TARGETS, which contains onlyretry.py. The declared serving modules are never mutated — and cannot be: they all transitively import duckdb, and duckdb's compiled subpackage_duckdb._sqltypesfails to import inside mutmut'smutants/workspace ('_duckdb' is not a package), crashing the run with every mutant leftnot checked.Reproduced in a Linux container (
python:3.11), so this is a mutmut × duckdb harness limitation, not platform-specific.retry.pyworks precisely because it is duckdb-free; duckdb itself imports fine under normal pytest (the full suite passes) — only mutmut's workspace breaks it.Without this note, the policy test reads as if the security modules are mutation-covered when they are not (false assurance).
Change
Comments only, at the three places a reader meets the claim —
pyproject.toml [tool.mutmut], the runner'sMODULE_TARGETS, andtest_mutmut_policy.py. No logic change.Verification
ruff check+ruff format --check: cleanpytest tests/unit/test_mutmut_policy.py tests/unit/test_mutation_report.py: 5 passedFollow-up (not in this PR)
Extending the gate to serving modules needs isolated mutant execution (subprocess/spawn) or a different mutation tool (e.g. cosmic-ray / mutatest) — a separate, CI-affecting decision.
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