fix(ci): economyEngine.test.js worker-IPC-flake — deterministisk isolation (#3172) (#3222)

* fix(ci): isolate economyEngine.test.js to stop worker-IPC flake

backend/lib/economyEngine.test.js is by far the largest backend test
file (100+ tests, 6500+ lines, ~250KB) and its per-worker result
payload appears large enough to trip a known Node test-runner bug
(nodejs/node#64061, root-caused and fixed upstream in
nodejs/node#64706, merged 2026-07-26 but not yet in our pinned Node
24.x line) when many other test-file workers stream results back to
the parent process concurrently. Isolated runs were always
102/102 (now 103/103) green; the flake only ever showed up in the
full suite (#3169-CI, #3171-CI).

Add backend/scripts/run-tests.js: runs economyEngine.test.js alone
first, then every other backend test file exactly as before (same
flags, same default concurrency) via explicit relative file paths so
the two passes never overlap. Wire both npm test (backend/package.json
- the one permitted package.json edit) and scripts/verify-local.ps1
(which called `node --test` directly, bypassing npm entirely) through
this script so CI and local pre-push runs get the same protection.

No dependency or lockfile changes. Verified with 5 consecutive
`npm test` runs locally (103/103 + 4773/4773 every time, exit 0).

Refs #3172
Co-Authored-By: Claude <noreply@anthropic.com>

* docs(learnings): postmortem for economyEngine.test.js worker-IPC flake

Refs #3172
Co-Authored-By: Claude <noreply@anthropic.com>

---------

Co-authored-by: Nicolai Dolmer <213100469+NicolaiDolmer@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>

Author: NicolaiDolmer

.claude/learnings/2026-08-03-economy-test-worker-ipc-flake.md

@@ -0,0 +1,63 @@
+# Postmortem · 2026-08-03 · economyEngine.test.js worker-IPC-flake (#3172)
+
+## Hvad skete der?
+`backend-tests`-CI-jobbet fejlede 2x samme dag (31/7, #3169 og #3171) med præcis
+1 fejlende fil: `lib/economyEngine.test.js`, med en runner-intern fejl
+`Unable to deserialize cloned data due to invalid or unsupported version`
+(`node:internal/test_runner`). Alle 102/102 testcases i filen var grønne når
+filen kørte isoleret, og resten af suiten (4729/4730) var grøn. Set lokalt i
+`scripts/verify-local.ps1` 31/7 også — ikke PR-specifikt.
+
+## Root cause
+`economyEngine.test.js` er langt den største backend-testfil (103 tests,
+6513 linjer, ~250KB — mere end dobbelt så stor som næststørste fil,
+`auctionFinalization.test.js` på 2753 linjer). Node's testrunner starter én
+child-worker pr. testfil og streamer testresultater tilbage til
+parent-processen via IPC (structured clone over en socket). Med 344
+testfiler kører op til ~8 workers samtidigt (CPU-parallelisme). Den store
+fils resultat-payload er tilsyneladende stor nok til at ramme en kendt
+buffer-parsing-bug i Node's testrunner (`nodejs/node#64061`): en
+signed/unsigned-fejl i `processRawBuffer`, rettet upstream i
+`nodejs/node#64706` (merged 2026-07-26) — men den rettelse er endnu ikke i
+vores pinnede Node 24.x-linje (`engines: >=24.0.0 <25`, lokal `v24.16.0`).
+Bugklassen trigges kun ved samtidig IPC-trafik fra mange workers, hvilket
+forklarer hvorfor filen ALTID er grøn isoleret og KUN flaker i fuld suite.
+
+## Fix
+`backend/scripts/run-tests.js` (nyt): kører `lib/economyEngine.test.js`
+alene i pass 1 (ingen samtidig worker-trafik at kollidere med), derefter alle
+øvrige ~343 testfiler i pass 2 med samme flags/default-concurrency som før,
+via eksplicitte RELATIVE filstier (ikke absolutte — 344 absolutte stier
+rammer Windows' ~32.767-tegns CreateProcess-kommandolinjegrænse og
+`spawnSync` fejler med `ENAMETOOLONG`; relative stier er ~10.500 tegn, rigelig
+margin). CLI-args (`--test-reporter=spec`) videreføres til begge pass.
+
+`backend/package.json`: `"test"` peger nu på `node scripts/run-tests.js`
+(den ene tilladte package.json-undtagelse — ingen dependency-/lockfile-ændring).
+
+`scripts/verify-local.ps1`: kaldte tidligere `node --test` DIREKTE (uden om
+npm og uden `--import ./test-setup.js`) — opdateret til at kalde samme
+`run-tests.js`, så lokale pre-push-kørsler får samme beskyttelse (den var
+netop hvor flaket også blev set 31/7).
+
+Ingen dependency- eller package-lock.json-ændringer. Ingen blind retry —
+den valgte løsning fjerner selve race-betingelsen (samtidighed) i stedet for
+at maskere en lejlighedsvis fejl.
+
+## Forhindret-fremover
+Stress-verificeret med 5 på hinanden følgende `npm test`-kørsler lokalt:
+103/103 + 4773/4773 grønt, exit 0, hver gang — ingen deserialize-fejl.
+Acceptkriteriet fra #3172 (2 ugers flake-fri CI på denne signatur) verificeres
+efterfølgende i CI over tid.
+
+## Læring
+En enkelt unormalt stor testfil i en ellers homogen testsuite er ikke kun et
+læsbarheds-/vedligeholdelsesproblem — den kan trigge infrastruktur-bugs
+(her: Node's eget testrunner-IPC) som kun viser sig under samtidighed, aldrig
+isoleret. Når en test-only-fejl er 100% reproducerbar i fuld suite og 0%
+isoleret, er "kør den isoleret" (test-script-niveau isolation) ofte den mest
+målrettede fix — billigere og mere deterministisk end en Node-version-bump
+eller en retry-wrapper, og den fjerner selve race-betingelsen frem for at
+maskere den. Bonus-gotcha: pas på Windows' kommandolinjelængde-grænse
+(~32K tegn) når man bygger en eksplicit filliste til `spawnSync`/`execFile` —
+brug relative stier, ikke absolutte, med mange filargumenter.

backend/package.json

@@ -27,7 +27,7 @@
     "balance:baseline": "node scripts/balanceBaseline.js --write",
     "season:end:verify-repair": "node scripts/verifySeasonEndRepair.js",
     "board:repair-members-after-dna": "node scripts/repairBoardMembersAfterDna.js",
-    "test": "node --test --import ./test-setup.js",
+    "test": "node scripts/run-tests.js",
     "lint": "eslint .",
     "lint:fix": "eslint . --fix",
     "format": "prettier --write --ignore-unknown .",

backend/scripts/run-tests.js

@@ -0,0 +1,88 @@
+// #3172: node:internal/test_runner intermittently corrupts worker-IPC data
+// ("Unable to deserialize cloned data due to invalid or unsupported version")
+// only when MANY test-file workers stream results back to the parent test
+// runner process at the same time. Root cause upstream: nodejs/node#64061,
+// fixed by nodejs/node#64706 (merged 2026-07-26) — a signed/unsigned bug in
+// the test runner's internal `processRawBuffer` that mishandles large IPC
+// buffers. That fix has not reached our pinned Node 24.x line yet, so we
+// isolate the offending file instead of waiting on a Node bump.
+//
+// lib/economyEngine.test.js is by far the largest backend test file (100+
+// top-level tests, 6500+ lines, ~250KB) — its per-worker result payload is
+// large enough to be the one that trips the bug when it lands concurrently
+// with the other ~340 test-file workers. Isolated runs of the file are
+// 102/102 green every time; the flake has only ever been observed in the
+// full suite (#3169-CI, #3171-CI).
+//
+// Fix: run the large file alone FIRST (no concurrent worker traffic to race
+// against), then run every other backend test file exactly as before (same
+// flags, same default concurrency). Any CLI args npm forwards (e.g.
+// `--test-reporter=spec` from `npm test -- --test-reporter=spec`) are passed
+// through to both passes unchanged.
+//
+// Deliberately NOT using `--test-concurrency=1` for the whole suite: that
+// would serialize all ~344 files and materially slow down CI/local runs for
+// a bug that only needs ONE file kept out of the concurrent pool.
+import { spawnSync } from "node:child_process";
+import { readdirSync } from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+
+const backendRoot = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
+const ISOLATED_RELATIVE = path.join("lib", "economyEngine.test.js");
+const IGNORED_DIRS = new Set(["node_modules", ".git"]);
+
+function findTestFiles(dir, out) {
+  for (const entry of readdirSync(dir, { withFileTypes: true })) {
+    if (entry.isDirectory()) {
+      if (IGNORED_DIRS.has(entry.name)) continue;
+      findTestFiles(path.join(dir, entry.name), out);
+    } else if (entry.isFile() && entry.name.endsWith(".test.js")) {
+      out.push(path.join(dir, entry.name));
+    }
+  }
+  return out;
+}
+
+function runNodeTest(extraArgs, files) {
+  const result = spawnSync(
+    process.execPath,
+    ["--test", "--import", "./test-setup.js", ...extraArgs, ...files],
+    { stdio: "inherit", cwd: backendRoot },
+  );
+  if (result.error) throw result.error;
+  return result.status ?? 1;
+}
+
+const extraArgs = process.argv.slice(2);
+const isolatedAbsolute = path.join(backendRoot, ISOLATED_RELATIVE);
+const allTestFilesAbsolute = findTestFiles(backendRoot, []).sort();
+
+if (!allTestFilesAbsolute.includes(isolatedAbsolute)) {
+  // Guard-fail loudly rather than silently running everything together —
+  // if the file moves/renames, this script must be updated with it.
+  console.error(
+    `run-tests.js: expected isolated file not found at ${ISOLATED_RELATIVE} (#3172 guard). ` +
+      "Update backend/scripts/run-tests.js if the file moved or was renamed.",
+  );
+  process.exit(1);
+}
+
+// Relative paths, not absolute: with ~340 files, an absolute-path argv (this
+// worktree's path alone is ~65 chars) blows past Windows's ~32K CreateProcess
+// command-line limit and spawnSync fails with ENAMETOOLONG. Relative paths
+// (cwd is already backendRoot) cut the argv to a third of that, with plenty
+// of headroom as the suite grows.
+const restFilesRelative = allTestFilesAbsolute
+  .filter((file) => file !== isolatedAbsolute)
+  .map((file) => path.relative(backendRoot, file));
+
+console.log(`\n[run-tests] Pass 1/2: ${ISOLATED_RELATIVE} in isolation (#3172 worker-IPC flake guard)\n`);
+const isolatedStatus = runNodeTest(extraArgs, [ISOLATED_RELATIVE]);
+if (isolatedStatus !== 0) {
+  process.exit(isolatedStatus);
+}
+
+console.log(`\n[run-tests] Pass 2/2: remaining ${restFilesRelative.length} backend test files\n`);
+const restStatus = runNodeTest(extraArgs, restFilesRelative);
+process.exit(restStatus);

scripts/verify-local.ps1

@@ -51,7 +51,10 @@ if ($normalizedResolvedRoot -ne $repoRoot) {
 Write-Host "[1/3] Backend tests"
 Push-Location (Join-Path $repoRoot "backend")
 try {
-  & $nodePath --test
+  # #3172: brug samme scripts/run-tests.js som `npm test`, ikke rå `node --test`
+  # — koerer lib/economyEngine.test.js isoleret foerst for at undgaa
+  # worker-IPC-flaket (node:internal/test_runner, ramte ogsaa her 31/7).
+  & $nodePath scripts/run-tests.js
   if ($LASTEXITCODE -ne 0) {
     exit $LASTEXITCODE
   }