[verified] test(desktop): guard nonblocking runtime probes

(cherry picked from commit ee61bbfa311a0a99a1f8c14c18e3cdc97e51f3d1)

apps/desktop/electron/backend-probes.test.ts

@@ -7,6 +7,7 @@
 
 import assert from 'node:assert/strict'
 import fs from 'node:fs'
+import net from 'node:net'
 import os from 'node:os'
 import path from 'node:path'
 
@@ -15,6 +16,7 @@ import { test } from 'vitest'
 import {
   canImportHermesCli,
   DEFAULT_PROBE_TIMEOUT_MS,
+  execProbe,
   hermesRuntimeImportProbe,
   PROBE_TIMEOUT_MS,
   resolveProbeTimeoutMs,
@@ -29,6 +31,40 @@ import {
 // (a tiny script we write to disk that exits 0 on --version).
 const NODE_BIN = process.execPath
 
+test('execProbe keeps the parent event loop available to the child', async () => {
+  const server = net.createServer((socket) => socket.end('pong'))
+
+  await new Promise<void>((resolve, reject) => {
+    server.once('error', reject)
+    server.listen(0, '127.0.0.1', resolve)
+  })
+
+  const address = server.address()
+  assert.ok(address && typeof address === 'object')
+
+  const childScript = `
+    const net = require('node:net')
+    let reply = ''
+    const socket = net.createConnection(${address.port}, '127.0.0.1')
+    socket.setEncoding('utf8')
+    socket.on('data', (chunk) => { reply += chunk })
+    socket.on('end', () => process.exit(reply === 'pong' ? 0 : 1))
+    socket.on('error', () => process.exit(1))
+  `
+
+  try {
+    await execProbe(NODE_BIN, ['-e', childScript], {
+      stdio: 'ignore',
+      timeout: 1_000,
+      windowsHide: true
+    })
+  } finally {
+    await new Promise<void>((resolve, reject) => {
+      server.close((error) => (error ? reject(error) : resolve()))
+    })
+  }
+})
+
 test('canImportHermesCli returns false when path is falsy', async () => {
   assert.equal(await canImportHermesCli(''), false)
   assert.equal(await canImportHermesCli(null), false)