From 8f4ca5c73eade3457325b887c16858c1029d395e Mon Sep 17 00:00:00 2001
From: sneak <sneak@sneak.berlin>
Date: Sun, 1 Nov 2026 23:21:46 +0000
Subject: [PATCH] test: make test fails when jest force-stops a worker (closes
 #711)

When a test leaves a timer running, jest force-stops the worker that ran
the test, prints a warning, and the run still passes. Jest has no option
that fails the run instead. Both test scripts in package.json now run
jest through script/lib/jest.js. Jest runs inside that file's process,
so its terminal output stays the same. The file exits 1 when jest
printed that warning.

Model: opus-5-5
---
 eslint.config.js   |  3 +--
 package.json       |  4 ++--
 script/lib/jest.js | 40 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 43 insertions(+), 4 deletions(-)
 create mode 100644 script/lib/jest.js

diff --git a/eslint.config.js b/eslint.config.js
index f834c06..1c420d5 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -153,8 +153,7 @@ module.exports = [
         },
     },
 
-    // The helpers the script/ entrypoints call: plain node programs too, run
-    // from a shell script rather than from yarn, and never bundled.
+    // The files in script/lib/ run on plain node too, and are never bundled.
     {
         files: ["script/lib/**/*.js"],
         languageOptions: {
diff --git a/package.json b/package.json
index b61275e..2080619 100644
--- a/package.json
+++ b/package.json
@@ -6,8 +6,8 @@
     "license": "GPL-3.0",
     "private": true,
     "scripts": {
-        "test": "jest --maxWorkers=3",
-        "test:verbose": "jest --maxWorkers=3 --verbose",
+        "test": "node script/lib/jest.js --maxWorkers=3",
+        "test:verbose": "node script/lib/jest.js --maxWorkers=3 --verbose",
         "build": "node build.js",
         "lint": "eslint . && prettier --check .",
         "fmt": "prettier --write .",
diff --git a/script/lib/jest.js b/script/lib/jest.js
new file mode 100644
index 0000000..96ba5dc
--- /dev/null
+++ b/script/lib/jest.js
@@ -0,0 +1,40 @@
+// Runs jest with the arguments it is given, and fails the run when jest had to
+// force-stop the worker process that ran a test file. Jest itself only prints a
+// warning when that happens, and its run still passes. The warning means a test
+// left a timer or another open handle running. The test scripts in package.json
+// run jest through this file.
+//
+// Jest runs inside this process and writes to the terminal directly, so its
+// output looks the same as a plain jest run. This file only checks each write
+// to stderr for the warning below.
+
+"use strict";
+
+// The start of the warning that jest prints on stderr after it force-stops a
+// worker process.
+const WORKER_WARNING = "A worker process has failed to exit gracefully";
+
+let forceStopped = false;
+
+const writeStderr = process.stderr.write.bind(process.stderr);
+process.stderr.write = (chunk, ...rest) => {
+    if (String(chunk).includes(WORKER_WARNING)) {
+        forceStopped = true;
+    }
+    return writeStderr(chunk, ...rest);
+};
+
+// Runs after jest has finished, as the process exits.
+process.on("exit", () => {
+    if (forceStopped) {
+        console.error(
+            "script/lib/jest.js: failing the run, because jest force-stopped " +
+                "a worker process. A test left a timer or another open " +
+                "handle running.",
+        );
+        process.exitCode = 1;
+    }
+});
+
+// Jest's own command-line program. It reads its arguments from process.argv.
+require("jest/bin/jest");