Add mutation testing analysis and configuration#56
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Ran cargo-mutants against the full workspace (788 mutants tested, 367 missed, 389 caught, 30 unviable, 2 timeouts). MUTANTS.md documents the findings. The headline result is that eleven individual chain-verification check functions (time validity, basic constraints, critical extensions, duplicate extensions, name constraint placement, name constraint enforcement, keyCertSign, RFC 5280 strict rules, CRL strict rules, and the entire WebPKI policy layer) can be replaced with no-ops without any test failing. The existing negative tests fail for multiple reasons at once, so disabling any single check goes unnoticed. Other gaps: ip_matches_constraint / email_matches_constraint can be hard-coded true; the dns_names() / ip_addresses() / curve() convenience methods are entirely untested; DN special-character escaping and the DateTime month table have no coverage. Also adds: - .cargo/mutants.toml excluding CLI color helpers, the base64 line-wrap loop (mutations create infinite loops), and host- filesystem-dependent trust-store discovery. - /mutants.out* to .gitignore.
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Summary
This PR adds comprehensive mutation testing analysis and configuration to improve test coverage visibility and guide future testing efforts.
Changes
Added
MUTANTS.md: A detailed mutation testing report generated bycargo-mutantsthat documents:xcert-lib)curve(),dns_names(),ip_addresses())Added
.cargo/mutants.toml: Configuration to exclude known non-testable code from future mutation runs:base64_wrapfunction (mutations cause infinite loops)Updated
.gitignore: Added/mutants.out*to ignore mutation testing output artifactsNotable Findings
The analysis reveals that while individual parsing and utility functions are well-tested, the verification pipeline has significant gaps:
The report provides actionable guidance for improving test coverage, with the highest priority being per-check negative tests for the verification pipeline.
https://preview.claude.ai/code/session_01QYgbDNhxKkJi6qg2cQqWaN