test(vercel#39993): add a failed case

test/integration/script-loader/base/next.config.js

@@ -0,0 +1,3 @@
+module.exports = {
+  reactStrictMode: true,
+}

test/integration/script-loader/base/pages/page10.js

@@ -0,0 +1,23 @@
+import Script from 'next/script'
+import Link from 'next/link'
+
+if (typeof window !== 'undefined') {
+  window.onReadyCalls ??= 0
+}
+
+const Page = () => {
+  return (
+    <div className="container">
+      <Link href="/page9">Page 9</Link>
+      <div id="text"></div>
+      <Script
+        src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.1/jquery.min.js"
+        onReady={() => {
+          window.onReadyCalls++
+        }}
+      />
+    </div>
+  )
+}
+
+export default Page

test/integration/script-loader/test/index.test.js

@@ -8,6 +8,9 @@ import {
   stopApp,
   nextBuild,
   waitFor,
+  findPort,
+  launchApp,
+  killApp,
 } from 'next-test-utils'
 import webdriver from 'next-webdriver'
 import cheerio from 'cheerio'
@@ -214,6 +217,27 @@ describe('Next.js Script - Primary Strategies', () => {
     }
   })
 
+  // https://github.com/vercel/next.js/issues/39993
+  it('onReady should only fires once after load event in dev mode (issue #39993)', async () => {
+    let browser
+    // we will start a dedicated dev server for this test case only (scoped)
+    let devAppPort
+    let devApp
+
+    try {
+      devAppPort = await findPort()
+      devApp = await launchApp(appDir, devAppPort)
+      browser = await webdriver(devAppPort, '/page10')
+
+      // wait for jQuery to be loaded
+      await waitFor(1000)
+      expect(await browser.eval(`window.onReadyCalls`)).toBe(1)
+    } finally {
+      if (browser) await browser.close()
+      if (devApp) await killApp(devApp)
+    }
+  })
+
   it('priority beforeInteractive with inline script', async () => {
     const html = await renderViaHTTP(appPort, '/page5')
     const $ = cheerio.load(html)