mkl-write-regression is agent-read markdown (skill) from 00200200/maintainer-skills-lab: Write a focused regression test from an established bug reproduction and public behavior. Use when a fix needs a test that fails on the affected version; avoid mirroring the implementation or weakening assertions..
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What the file says
# Write a regression test
Read the reproduction, expected public behavior, and nearby test conventions. Derive the assertion from the behavior a caller needs, not from the proposed implementation.
Write the smallest test that captures the defect. Use deterministic inputs and existing project dependencies where practical. Do not mock away the faulty path. Place supporting fixtures beside the test and explain any environment requirements.
Run the test against the affected implementation before accepting it as a regression test. Inspect why it failed: an assertion about the reported behavior is evidence; an import error, collection failure, permission problem, or timeout is not the intended proof. Keep the test unchanged when evaluating the fix.
If the fix is already present, use an isolated checkout or an equivalent preserved baseline to test the pre-fix version. Preserve the user's current checkout and uncommitted work. Do not revert their working tree merely to get a red test.
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Pin to a label to follow the author's releases, or to a sha256 to freeze the exact bytes forever. Either way the resolved hash is written to mdr.lock, and mdr install reproduces it on any machine.
GET https://markdownregistry.com/api/v1/artifacts/art_ew3najpxmvnvll3o
GET https://markdownregistry.com/api/v1/resolve?ref=00200200/maintainer-skills-lab/mkl-write-regression
GET https://markdownregistry.com/api/v1/blob/173b1a4b9e1b113af455f3d4097693fe5f1a432ddd24c89ce76aada23850ecca
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