test(coverage): ratchet the unit region floors to the 100% scripts/ and src/ already measure

AGENTS.md

@@ -37,7 +37,7 @@ Before opening a PR, read
 [`CONTRIBUTING.md#making-changes`](CONTRIBUTING.md#making-changes) for the full
 fork/branch/PR process. Two CI-enforced requirements to note up front: the
 "Validate repository" check runs `npm run test:unit:coverage:check` (coverage
-thresholds 99% lines / 100% source / 95% regions / 99% source regions) on every
+thresholds 99% lines / 100% source / 96% regions / 100% source regions) on every
 PR, and every commit must carry a DCO `Signed-off-by` trailer (`git commit -s`)
 or CI will fail the PR.
 
@@ -50,8 +50,8 @@ or CI will fail the PR.
 - **Build**: `npm run build`
 - **Unit Tests**: `npm run test:unit:coverage:check` — required "Validate
   repository" CI check on every PR; enforces coverage thresholds (99% lines /
-  100% source / 95% regions / 99% source regions), plus separate floors for the
-  `tests/tools/` harness (100% lines / 97% regions, 93% regions per harness
+  100% source / 96% regions / 100% source regions), plus separate floors for the
+  `tests/tools/` harness (100% lines / 97% regions, 97% regions per harness
   file). `npm run test:unit` alone skips the coverage gate.
 - **End-to-end Tests**: required "End-to-end tests" CI check on every PR. Needs
   a production build first, then a one-time browser install:

CONTRIBUTING.md

@@ -177,9 +177,9 @@ enough for a first contribution.
 2. Make your change and run the relevant validation script.
 3. Run `npm run test:unit:coverage:check` — the required "Validate repository"
    check runs this on every PR, and it fails the build if unit-test coverage
-   drops below its thresholds (99% lines / 100% source / 95% regions / 99%
+   drops below its thresholds (99% lines / 100% source / 96% regions / 100%
    source regions). The harness under `tests/tools/` is floored separately (100%
-   lines / 97% regions, and 93% regions per harness file): it is measured like
+   lines / 97% regions, and 97% regions per harness file): it is measured like
    source but reported in its own `harness files` row, so a gap in the test
    apparatus cannot be paid for out of `src/`'s slack. `npm run test:unit` alone
    skips the coverage gate, so a green `test:unit` locally does not guarantee a

package.json

@@ -70,7 +70,7 @@
     "pr-queue-hygiene": "node scripts/pr-queue-hygiene.mjs",
     "test:unit": "TZ=UTC node --test",
     "test:unit:coverage": "TZ=UTC node tests/tools/coverage-report.mjs",
-    "test:unit:coverage:check": "TZ=UTC node tests/tools/coverage-report.mjs --check 99 --check-source 100 --check-regions 95 --check-source-regions 99 --check-source-file-regions 97 --check-harness 100 --check-harness-regions 97 --check-harness-file-regions 97 --require-source-files",
+    "test:unit:coverage:check": "TZ=UTC node tests/tools/coverage-report.mjs --check 99 --check-source 100 --check-regions 96 --check-source-regions 100 --check-source-file-regions 100 --check-harness 100 --check-harness-regions 97 --check-harness-file-regions 97 --require-source-files",
     "test:e2e": "playwright test",
     "build:e2e:coverage": "npm run build:e2e:coverage:site && npm run build:e2e:coverage:fixtures",
     "build:e2e:coverage:site": "DOCUSAURUS_NO_PERSISTENT_CACHE=1 E2E_COVERAGE=1 npm run build:production",

tests/coverage-gate-thresholds.test.mjs

@@ -28,36 +28,59 @@ const GATE_SCRIPT = 'test:unit:coverage:check';
 
 // Measured on the suite this commit ships, floored to a whole percent so a
 // rounding difference between runs cannot fail the build:
-//   all files   99.42% lines / 95.07% regions  (48197/48476 lines, 8060/8478 regions)
-//   src files  100.00% lines / 99.96% regions  (8721/8721 lines, 2475/2476 regions)
+//   all files    99.65% lines / 96.14% regions  (58948/59153 lines, 9515/9897 regions)
+//   src files   100.00% lines / 100.00% regions (9233/9233 lines, 2777/2777 regions)
 //
-// Only `--check-regions` has cleared a whole percent since the floors were
-// last set; the other three sit under their next whole percent (99.42, 99.96)
-// or are already at 100, so flooring leaves them where they are.
+// Both figures were taken twice, on node v22.21.1 -- the major ci.yml pins --
+// and on node v26.10.0, and the two runs agree to the region. Region counts
+// are a V8 artifact, so a floor set at exactly 100 is only safe once it has
+// been shown not to move with the runtime; these did not.
+//
+// `--check` sits under its next whole percent (99.65) and `--check-source` is
+// already at 100, so flooring leaves both where they are. The three region
+// floors below have all cleared a whole percent since they were last set.
 const FLOORS = {
   '--check': 99,
   '--check-source': 100,
-  '--check-regions': 95,
-  '--check-source-regions': 99,
+  '--check-regions': 96,
+  // scripts/ and src/ are at 2777/2777: every region executed, with no
+  // uncreditable residual of the kind that keeps the browser gate (#1256) and
+  // the harness per-file gate below their own ceilings. 100 is therefore the
+  // measured floor here rather than an aspiration. A new defensive fallback in
+  // either tree now has to be reached by a test or argued for by lowering this
+  // deliberately -- which is the point: at 99 the gate let 27 source regions
+  // go dark before it noticed.
+  '--check-source-regions': 100,
   // Per-file rather than aggregate, so its floor is set by the worst source
   // file rather than by the whole of scripts/ and src/ together. Measured on
-  // the suite this commit ships, the lowest is
-  // scripts/lib/architecture-content.mjs at 97.78%, floored to 97.
-  '--check-source-file-regions': 97,
+  // the suite this commit ships, every file under both trees is at 100.00%,
+  // so the worst is 100. Kept alongside the aggregate even though an aggregate
+  // of 100 implies it: the per-file check is what names the offending file and
+  // its uncovered regions in the failure message.
+  '--check-source-file-regions': 100,
   // The harness tree (tests/tools/) is walked by --require-source-files and
   // entered none of the ratios above, which are all built from
   // isSourceFile(). These are the same three shapes over its own row.
   // Measured on the suite this commit ships: harness files 100.00% lines /
-  // 99.53% regions (3925/3925 lines, 1467/1474 regions), and the lowest
-  // harness file is tests/tools/e2e-coverage-report.mjs at 98.57%, floored
-  // to 97. Every other harness file is at 100.00%.
+  // 99.57% regions (5336/5336 lines, 1867/1875 regions), now that #1294 has
+  // brought tests/helpers*.mjs into the row. The lowest harness file is
+  // tests/helpers-script-sandbox.mjs at 97.06%, floored to 97; next is
+  // tests/tools/e2e-coverage-report.mjs at 98.57%, and every other harness
+  // file is at 100.00%.
+  //
+  // 98.57% is e2e-coverage-report.mjs's ceiling, not a backlog: its 7
+  // uncovered regions are the defensive fallbacks the note at the top of the
+  // file lists as unreachable (#1253; three more were deleted rather than
+  // listed in #1304), so no test can lift it. The per-file floor must stay at
+  // or below 97 while helpers-script-sandbox.mjs sits at 97.06, and at or
+  // below 98 until that list shrinks; a probe that lands one of them should
+  // raise the floor and shorten the list in the same change.
   //
-  // 98.57% is also that file's ceiling, not a backlog: its 7 uncovered
-  // regions are the defensive fallbacks the note at the top of the file lists
-  // as unreachable (#1253; three more were deleted rather than listed in
-  // #1304), so no test can lift it. The per-file floor must stay at or below
-  // 98 until that list shrinks; a probe that lands one of them should raise
-  // the floor and shorten the list in the same change.
+  // --check-harness-regions is left at 97 against a measured 99.57 on purpose:
+  // #1294 only just rescoped the row, and the helper tree's lowest file is
+  // 0.06 points above the per-file floor, so the aggregate is left with its
+  // slack until that file has been lifted rather than ratcheted into a gate
+  // the next helper edit trips.
   '--check-harness': 100,
   '--check-harness-regions': 97,
   '--check-harness-file-regions': 97,