feat(ci): promtool in the pinned toolchain, one alert-rule harness, and the gaps declared

The CNPG alert unit tests (324 lines, mutation-checked) were run by NOTHING. promtool was
not in the baked toolchain, no gate stage evaluated any *.promtool-test.yaml, and the only
runner `curl | tar -xz`'d a promtool release from GitHub at TEST-RUN time if one was
missing. Hours later a second, independent harness landed for the Velero rules
(platform/monitoring/tests/) with its own fallback — a `podman run` of
quay.io/prometheus/prometheus. So the repo had two harnesses, two acquisition paths, and
coverage that looked present and was enforced nowhere: the exact failure mode that had just
produced a permanently-firing CNPG alert and a structurally inert Velero alert.

PROMTOOL IS NOW PINNED LIKE EVERY OTHER TOOL. PROMTOOL_VERSION=3.14.0 in
infra/devcontainer/versions.env and ci/versions.env (the two stay in lockstep, per the
repo's rule), baked by the Containerfile from the prometheus release tarball (promtool ships
inside it), recorded in /etc/dev-toolchain-versions, passed by dev.sh, and installed for the
l0 stage by .gitea/workflows/scripts/install-tools.sh so the CI runner is not permanently
SKIPPED. The pin is not free-floating: promtool IS the rule engine, so it tracks the
Prometheus prod actually runs — verified against the live cluster, not assumed:

    kubectl --context k3s-prod get prometheus -n monitoring -o jsonpath='{.items[*].spec.version}'
      -> v3.14.0-distroless   (image quay.io/prometheus/prometheus:v3.14.0-distroless)

ONE HARNESS. platform/cnpg/run-alert-tests.sh is folded into
platform/monitoring/tests/run.sh, which now covers every PrometheusRule in the repo that has
tests, via two conventions it discovers automatically: `<manifest>.promtool-test.yaml`
beside its manifest (cnpg), and `<component>/tests/*.test.yaml` over that component's
manifests (monitoring). It writes the flattened rules under whatever name each test file's
own `rule_files:` declares, so no test file needs to know the harness exists, and it
`promtool check rules` first — a rules file that does not parse would make every unit test
pass vacuously by finding no rules at all. The cnpg script's reasoning is preserved: why a
CR must be flattened (`.spec.groups`, never re-typed), and why generated files go to a temp
dir. Its `${BASE_DOMAIN}` substitution is dropped in favour of extract_rules.py's verbatim
placeholders, with the trade-off recorded there — the hazard it guarded against is addressed
by the temp dir, and verbatim leaves one transformation fewer between the shipped rule and
the rule under test.

NO ENGINE IS ACQUIRED AT RUN TIME any more — not the GitHub release, not the container
image. Not because a pinned download is unusual here (the Containerfile downloads every tool
it bakes) but because those two decided the version, the network and the machine SILENTLY,
at test time, on whatever host ran the tests; and each quietly turned "the toolchain has no
promtool" into a green run, which is how the toolchain stayed without one. Missing promtool
is exit 3 (UNWIRED, never green); a PROMTOOL= that does not resolve is exit 2.

ONE WIRING: conformance/tests/l0-static/alert-rules-unit-tested, NOT a gate stage. The
`prom-rules` stage (ci/prom-rules.sh + its Makefile target + ci/gate.sh entry) is deleted:
it is the bespoke-per-check pattern b9f8807 had just removed from ci/l0.sh, and the
declarative replacement gives what a hand-written stage cannot — selection by
`conformance.home.k3s/scope: "whole-repo"` (asserted: the test is selected even under a
requirement filter matching nothing), requirement-attributed JUnit/coverage/ledger evidence,
and run_l1_offline.py's rule that a SKIP of a scope-declaring check is the runner's rc 3.
The scope declaration is load-bearing here: touched-requirements.sh keys apps/* to nothing
and platform/monitoring/* to R-OBS-01/02, never R-OBS-04, so a new untested PrometheusRule
would otherwise be gated by nothing.

The check asserts the pins and their lockstep, that the image bakes and records promtool,
that the promtool IN USE reports exactly the pin (a FAILURE, not a skip: the wrong engine
still prints SUCCESS), that exactly ONE harness exists and none fetches an engine, that
every rule-unit test file passes, and — on every run — that the harness CAN fail, by putting
a synthetic rule through it twice with one expectation mutated.

MISSING TESTS ARE A RATCHET, deliberately, and the reasoning is in the check's header. 51 of
58 alert rules have no unit test. Failing on all of them makes the gate red until ~51 tests
exist, so it gets disabled and protects nothing; merely reporting is exactly how the CNPG
tests came to be enforced by nothing. So the gap is DECLARED in the check as a shrink-only
register, printed with counts every run (13 alert files nothing tests at all; 35 named
alerts inside covered files that nothing asserts on), and it cannot grow: a new
PrometheusRule, or a new alert in an already-covered file, FAILS without a test, and a stale
entry FAILS too. A missing test is never an exit-3 skip — SKIPPED is reserved for the one
genuine environment gap, promtool being absent.

PROVEN, in the rebuilt image (promtool 3.14.0):
  * both suites pass through the single harness: cnpg 6 rules, monitoring 36 rules, SUCCESS.
  * the check passes: 95 assertions, 7/58 alert rules unit-tested, 13 declared gap files.
  * NOT VACUOUS, twice over. Shortening CNPGPrimariesCoLocated's `for: 30m` to 5m turns it
    red (pending expected at 25m/29m, got firing), reverted. Adding an untested
    PrometheusRule (platform/kubevirt/probe-alerts.yaml) turns it red on the ratchet,
    removed. The harness's own mutation self-test runs on every invocation.
  * the scope mechanism selects it: `run.sh --layer l0 --requirements r-nosuchreq-99
    --include-scope whole-repo --print-selection` lists alert-rules-unit-tested.

Co-Authored-By: Claude Opus 5 <[email protected]>

ci/Makefile

@@ -12,7 +12,7 @@ CI_DIR := $(dir $(abspath $(lastword $(MAKEFILE_LIST))))
 
 .DEFAULT_GOAL := help
 
-.PHONY: help spec-immutability lint schema l0 render-golden l1 prom-rules conformance gate all touched versions tools test
+.PHONY: help spec-immutability lint schema l0 render-golden l1 conformance gate all touched versions tools test
 
 help: ## Show this help
 	@awk 'BEGIN{FS=":.*##"} /^[a-zA-Z0-9_-]+:.*##/{printf "  \033[36m%-14s\033[0m %s\n",$$1,$$2}' $(MAKEFILE_LIST)
@@ -32,9 +32,6 @@ render-golden: ## render==golden: canonical render reproduces committed apps/ (n
 l1: ## L1 rendering checks (no cluster; live now)
 	@"$(CI_DIR)l1.sh"
 
-prom-rules: ## promtool rule-unit tests for platform/monitoring alerts (no cluster; live now)
-	@"$(CI_DIR)prom-rules.sh"
-
 conformance: ## L2/L3 in-cluster Chainsaw Job (SKIPS w/o CLUSTER_AVAILABLE=true)
 	@"$(CI_DIR)conformance.sh"
 

ci/README.md

@@ -22,7 +22,6 @@ Individual stages:
 make -C ci lint        # yaml/lint                          (no cluster; live now)
 make -C ci l0          # schema + Kyverno + L0 static conformance (no cluster; live now)
 make -C ci l1          # L1 rendering checks                 (no cluster; live now)
-make -C ci prom-rules  # promtool rule-unit tests on alerts  (no cluster; live now)
 make -C ci conformance # L2/L3 in-cluster Chainsaw Job       (SKIPS unless CLUSTER_AVAILABLE=true)
 make -C ci test        # unit tests for these scripts themselves (ci/tests/*.test.sh)
 ```
@@ -103,14 +102,13 @@ in that case — nothing goes untested — and says plainly that the *scoped* ch
 
 ```
 ci/
-  Makefile                 targets: lint · l0 · l1 · prom-rules · conformance · gate · touched · test · tools · versions
+  Makefile                 targets: lint · l0 · l1 · conformance · gate · touched · test · tools · versions
   versions.env             PINNED tool versions (R-TEST-02) — single source of truth
   lib.sh                   shared helpers: logging, tool checks, cluster detection, artifact paths
   yamllint.yaml            lint config for the yaml/lint stage
   lint.sh                  Stage: yaml/lint
   l0.sh                    Stage: schema validation + Kyverno L0 gate + L0 static conformance
   l1.sh                    Stage: L1 rendering checks (Chainsaw L1 via the conformance runner)
-  prom-rules.sh            Stage: `promtool test rules` over platform/monitoring's PrometheusRules
                            (harness: platform/monitoring/tests/). Catches the two alerting bugs no
                            other stage can see — permanently-firing and structurally INERT rules.
   conformance.sh           Stage: L2/L3 in-cluster Chainsaw Job (trigger + collect)

ci/gate.sh

@@ -42,7 +42,6 @@ run_stage lint          "${CI_DIR}/lint.sh"
 run_stage l0            "${CI_DIR}/l0.sh"
 run_stage render-golden "${CI_DIR}/render-golden.sh"
 run_stage l1            "${CI_DIR}/l1.sh"
-run_stage prom-rules    "${CI_DIR}/prom-rules.sh"
 run_stage conformance   "${CI_DIR}/conformance.sh"
 
 echo >&2
@@ -87,7 +86,7 @@ esac
 # Phase 0 that is tolerated (placeholders), but surfaced. render-golden is a
 # no-cluster reproducibility gate (canonical render == committed apps/ goldens):
 # a FAIL means a golden drifted from its ServiceDefinition source — always blocks.
-for s in lint l0 render-golden l1 prom-rules; do
+for s in lint l0 render-golden l1; do
   case "${OUTCOME[$s]}" in
     fail) err  "${s}: FAILED -> blocks merge"; BLOCK=1 ;;
     skip) warn "${s}: skipped (unwired seam / missing tool) — not green" ;;

ci/prom-rules.sh

@@ -1,44 +0,0 @@
-#!/usr/bin/env bash
-# ci/prom-rules.sh — Stage: Prometheus RULE-UNIT tests (no cluster; live now).
-#
-# Thin wrapper over platform/monitoring/tests/run.sh, which runs `promtool test rules` against the
-# COMMITTED PrometheusRule manifests. It is a gate stage because the two alerting defects this repo
-# has actually shipped — a permanently-firing rule and a structurally INERT one — are both invisible
-# to every other stage: yamllint parses them, Kyverno admits them, and a healthy cluster cannot tell
-# a correct alert from one that can never fire. Only the bad state, constructed on purpose, can.
-#
-# Exit codes per ci/lib.sh: 0 pass / 1 fail / 3 skipped (never green).
-set -euo pipefail
-CI_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-# shellcheck disable=SC1091
-source "${CI_DIR}/lib.sh"
-
-log "Stage: Prometheus rule-unit tests (promtool test rules; no cluster)"
-
-RUNNER="${REPO_ROOT}/platform/monitoring/tests/run.sh"
-if [ ! -x "$RUNNER" ]; then
-  skip "rule-unit harness not present at ${RUNNER} — UNWIRED, not green"
-  summary "- prom-rules: **SKIPPED** (harness missing)"
-  exit 3
-fi
-
-set +e
-"$RUNNER"
-rc=$?
-set -e
-
-case "$rc" in
-  0)
-    ok "Prometheus rule-unit tests passed"
-    summary "- prom-rules: **passed**"
-    ;;
-  3)
-    skip "promtool unavailable (no promtool on PATH, no podman/docker) — NOT green"
-    summary "- prom-rules: **SKIPPED** (promtool toolchain unavailable)"
-    ;;
-  *)
-    err "Prometheus rule-unit tests FAILED"
-    summary "- prom-rules: **FAILED**"
-    ;;
-esac
-exit "$rc"

ci/versions.env

@@ -21,6 +21,15 @@ YAMLLINT_VERSION="1.35.1"
 KUBECTL_VERSION="1.36.4"
 YQ_VERSION="4.44.6"
 
+# Alert-rule unit tests (promtool test rules) — the L0 check
+# conformance/tests/l0-static/alert-rules-unit-tested runs every
+# platform/**/*.promtool-test.yaml through it. MUST stay in lockstep with
+# infra/devcontainer/versions.env (which bakes it into the image) AND with the Prometheus
+# version running on prod, because promtool IS the rule engine: verified 2026-09-12 as
+# v3.14.0-distroless via `kubectl get prometheus -n monitoring -o jsonpath='{.items[*].spec.version}'`.
+# Shipped inside the prometheus release tarball, not as a separate release.
+PROMTOOL_VERSION="3.14.0"
+
 # ServiceDefinition JSON-Schema validation (schemas/validate.sh). Pip-installed;
 # pinned here so CI and a laptop validate against the exact same validator.
 CHECK_JSONSCHEMA_VERSION="0.29.4"