test: add test for notFound during streaming

test/e2e/app-dir/app/app/not-found/suspense/page.js

@@ -0,0 +1,41 @@
+import { Suspense } from 'react'
+import { notFound } from 'next/navigation'
+
+function createSuspenseyComponent(Component, { timeout = 0, expire = 10 }) {
+  let result
+  let promise
+  return function Data() {
+    if (result) return result
+    if (!promise)
+      promise = new Promise((resolve) => {
+        setTimeout(() => {
+          result = <Component />
+          setTimeout(() => {
+            result = undefined
+            promise = undefined
+          }, expire)
+          resolve()
+        }, timeout)
+      })
+    throw promise
+  }
+}
+
+function NotFound() {
+  notFound()
+  return <></>
+}
+
+const SuspenseyNotFound = createSuspenseyComponent(NotFound, {
+  timeout: 300,
+})
+
+export default function () {
+  return (
+    <div className="suspense">
+      <Suspense fallback="fallback">
+        <SuspenseyNotFound />
+      </Suspense>
+    </div>
+  )
+}

test/e2e/app-dir/index.test.ts

@@ -2359,6 +2359,20 @@ createNextDescribe(
             .getAttribute('content')
         ).toBe('noindex')
       })
+      it('should trigger not-found while streaming', async () => {
+        const initialHtml = await next.render('/not-found/suspense')
+        expect(initialHtml).not.toContain('noindex')
+
+        const browser = await next.browser('/not-found/suspense')
+        expect(
+          await browser.waitForElementByCss('#not-found-component').text()
+        ).toBe('Not Found!')
+        expect(
+          await browser
+            .waitForElementByCss('meta[name="robots"]')
+            .getAttribute('content')
+        ).toBe('noindex')
+      })
     })
 
     describe('bots', () => {