test-safety-net

Build the change-detector that unblocks agent work on an untested codebase. This is not a correctness audit: current behaviour gets pinned even where it looks wrong, and a suspected bug gets reported rather than silently blessed as correct. The output is a net that catches unintended behaviour change, plus an honest account of what it could not net and why — never a coverage percentage.

When to use

Reach for this when a repo has no meaningful tests and someone needs to change it safely: "I don't trust an agent in this codebase," "add tests before we refactor," "we need a safety net before this migration." It sits between two siblings and does neither of their jobs: verifier-installer installs the runnable verify→repair loop (format/build/test + CI) and stops at one placeholder test to keep the loop runnable — this skill fills that placeholder with real tests. clean-code then judges what comes out (clean-code/references/testing.md) and receives the seam list this skill cannot act on itself (see Tiers 3/4 below). Do not use this to chase a coverage number, to bless current behaviour as correct, or to refactor code to make it testable — that inverts the safety property the skill exists to provide (see Invariant 1).