# Quarantine as ratified contract, not hidden debt

> Some failing tests are not stale and not wrong — they assert behaviour the owner has ruled correct that simply hasn't been built yet. Deleting them loses the ruling; skipping them hides it. Move them verbatim into a quarantine directory whose integrity is itself spec-tested: immutable assertions, a header naming the owning work package, a hard cap on directory size, and no vacuous specs.

URL: https://biloh.com.au/docs/engineering-notes/quarantine-as-ratified-contract
Category: Engineering notes | Audience: builder | Updated: 2026-08-28

## The third kind of failing test

Triage a failing test and it lands in one of three buckets: the **test is stale** (the behaviour legitimately changed — fix the test), the **code is defective** (fix the code), or — the awkward one — the **test is right and the feature doesn't exist yet**. The assertion describes behaviour the product owner has explicitly ruled correct, but building it is a real work package, not an afternoon.

Delete that test and you delete a ratified decision. Mark it `.skip` and you hide a decision inside a mechanism built for flaky tests. Leave it red and it poisons the suite's signal. None of these survive an honest zero-failing-tests policy.

## The convention

Move the spec — **assertions preserved verbatim** — into a dedicated quarantine directory excluded from the suite run. Each file carries a header naming:

- the **work package** that owns building the behaviour,
- the **ruling** it encodes (who decided, and what they decided), and
- the **evidence** the ruling was based on.

The failing test stops counting against the suite, but nothing about it has been weakened: it is now a specification waiting for its build. When the work package lands, its definition of done is *the quarantined spec passes as written* and moves back into the suite. The team calls this building **red-first from a ratified contract** — the spec exists, measured red, before the first line of the feature.

## The quarantine is itself under test

A convention like this rots into a landfill unless something enforces it. A structural integrity lock — an ordinary test in the main suite — asserts:

- **Immutability**: quarantined assertions match the verbatim text recorded when they entered. Softening a spec inside quarantine is a build failure.
- **Ownership**: every file's header names a work package. Anonymous debt is refused.
- **A hard cap** on the number of quarantined specs. The cap forces a conversation ("build one out, or raise the cap deliberately") instead of unbounded quiet growth.
- **No vacuous specs**: a quarantined file with no real assertions fails the lock — a spec that asserts nothing specifies nothing.

The cap and the immutability rule are what distinguish this from a graveyard: the directory can only shrink through *builds*, never through erosion.

## A worked example

A billing-cadence defect surfaced as a failing test: a job completing late, after its period's consolidated invoice had already been drafted, was silently appended to that draft. The owner ruled the opposite: **a drafted invoice is stable once drafted; the late job rolls to the next period automatically.** The ruling became three quarantined specs — the drafted invoice is byte-identical before and after the late completion, the late line lands on the next period's draft with its exact cents, and the job is billed exactly once — each asserting exact database-level amounts. The work package that builds the routing inherits its acceptance tests ready-made, and cannot be declared done until specs it never wrote go green.

## Why not just a backlog ticket?

A ticket describes intent in prose; a quarantined spec *is* the acceptance test, with exact assertions, already agreed. Prose drifts and gets re-litigated; an immutable spec with a named ruling does not. The backlog ticket still exists — it points at the spec.

## Related

- [A failure ceiling that only goes down](/docs/engineering-notes/a-failure-ceiling-that-only-goes-down)
- [Freeze the baseline, then burn it down](/docs/engineering-notes/freeze-the-baseline-then-burn-it-down)
- [One home, locked in both directions](/docs/engineering-notes/one-home-locked-both-ways)