/ripwire-write-tests

name: ripwire-write-tests
description: >
  Write tests for EXISTING code that has none — 'this is untested, add coverage', 'add a safety
  net first'; also verify a new test reaches its intended code. Finds what no test reaches: --seams
  ranks untested cross-module edges, --callers gives the outside contract. Diff test selection →
  change-check. For one target one --seams or --callers pass suffices.
allowed-tools: Bash, Read

Writing tests with ripwire

> Routing: > • Vetting a diff you already wrote (does it have test cover) → **ripwire-change-check**. > • Judging whether your OWN code got better/worse → **ripwire-quality-bar**. > • Don't know which symbol is even the bug → **ripwire-find-bug**. > • Not sure which skill? → **ripwire-router**.

`<dir>` = repo root. This skill answers "what should I write a test for, and what does it need to cover" — not "is my diff safe" (that's change-check).

Find the gap

1. **Untested integration seams** — `ripwire <dir> --seams --legend=compact` → `<seams>` lists cross-module call edges no test reaches. These are the highest-value targets: a bug here crosses a boundary silently, and one test per seam buys the most coverage per line written. Scope with `<dir>` = a subsystem to focus the seam list. 2. **The `tested=1` coverage lens** — `ripwire <dir> --metrics --legend=compact --top-k=50` (or `--for="<area>"`, which carries the same lens inline) → `tested="1"` means an indexed test-path symbol transitively reaches this production symbol. On these explicit metric surfaces the attribute is omitted when no indexed test reaches it; the binary never prints a fabricated zero. Cross an omitted `tested` with `in=` (fan-in): a widely-relied-on function with no indexed safety net is a sharper priority than an uncovered leaf. Shell/subprocess test coverage remains outside the call graph, so absence is a structural finding, not proof that no external test exists. 3. **Pick the target** — prefer a seam over a symbol lacking `tested=1` when both are candidates; a seam test proves two modules cooperate correctly, a unit test on one function does not.

Write it with the right contract

4. **The contract from OUTSIDE** — `ripwire <dir> --callers=SYM --legend=compact` for the symbol you're testing. Callers show the preconditions and argument shapes callers actually rely on — write the test against that observed contract, not just the signature. 5. **The body, to know what branches exist** — `ripwire <dir> --expand=SYM --legend=compact` → full source + callee signatures. Cover the branches; don't just re-assert the happy path the caller already exercises.

Verify the test actually registers

6. **Confirm it's wired in** — `ripwire <dir> --affected=<the file you just changed> --legend=compact` should now list your new test file among the tests that transitively reach the changed code. If it doesn't show up, the test harness isn't discovering the new file (wrong naming convention, missing registration) — fix that before trusting the coverage. 6b. **Read what an existing test already covers** — `ripwire <dir> --exercises=test/<harness> --legend=compact` lists the non-test symbols that test transitively calls into, ranked. Use it before writing anything to avoid re-covering ground a neighbouring harness already holds, and use it as the first call when an existing test FAILS and you only have its name. (A non-test path refuses — the verb is the test/non-test partition; for "what does this file call", use `--callees`.) 7. **Close the loop with the gate** — once `--affected` proves the test registers, `ripwire <dir> --test-gate --legend=compact` on the symbol's file should now go green (the symbol drops out of the untested-blast-radius list). This is the same TDAD-parity gate **ripwire-change-check** runs before merge — writing the test here is what makes it pass there.

Output

Name the seam or symbol lacking `tested=1` chosen and why (seam > high-fan-in symbol > leaf), the contract drawn from `--callers`, and confirmation from `--affected` that the new test registers. Re-run `--seams`/`--metrics` afterward — the gap you targeted should be gone.