Purpose
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FS-508 regression coverage for the lint baseline (snapshot + diff).
Responsibilities
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- Validate save_baseline creates a file and returns a count.
- Validate load_baseline reads back saved data.
- Validate diff_against_baseline detects new and resolved violations.
- Validate --baseline and --against-baseline flag behaviour via run_linter.
- Validate mutually exclusive flag error.
Diagnostics
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Domain: LINTER-TESTS
Levels:
L2 — test lifecycle
L3 — assertion details
L4 — deep tracing
Contracts
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- All baseline files are written to ``tmp_path``; no real project
baselines are touched.