Add additional tests for prefetch and trailingSlash (#40517)

Adds some of the tests we didn't have yet for app.
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## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the
feature request has been accepted for implementation before opening a
PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `pnpm lint`
- [ ] The examples guidelines are followed from [our contributing
doc](https://github.com/vercel/next.js/blob/canary/contributing.md#adding-examples)

test/e2e/app-dir/app-prefetch/app/dashboard/layout.server.js

@@ -1,5 +1,5 @@
 export async function getServerSideProps() {
-  await new Promise((resolve) => setTimeout(resolve, 2000))
+  await new Promise((resolve) => setTimeout(resolve, 400))
   return {
     props: {
       message: 'Hello World',
@@ -9,7 +9,7 @@ export async function getServerSideProps() {
 export default function DashboardLayout({ children, message }) {
   return (
     <>
-      <h1>Dashboard {message}</h1>
+      <h1 id="dashboard-layout">Dashboard {message}</h1>
       {children}
     </>
   )

test/e2e/app-dir/app-prefetch/app/dashboard/page.server.js

@@ -9,7 +9,7 @@ export async function getServerSideProps() {
 export default function DashboardPage({ message }) {
   return (
     <>
-      <p>{message}</p>
+      <p id="dashboard-page">{message}</p>
     </>
   )
 }

test/e2e/app-dir/app-prefetch/app/page.server.js

@@ -2,7 +2,9 @@ import Link from 'next/link'
 export default function HomePage() {
   return (
     <>
-      <Link href="/dashboard">To Dashboard</Link>
+      <Link href="/dashboard">
+        <a id="to-dashboard">To Dashboard</a>
+      </Link>
     </>
   )
 }

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

@@ -23,15 +23,7 @@ describe('app dir', () => {
   function runTests({ assetPrefix }: { assetPrefix?: boolean }) {
     beforeAll(async () => {
       next = await createNext({
-        files: {
-          public: new FileRef(path.join(__dirname, 'app/public')),
-          styles: new FileRef(path.join(__dirname, 'app/styles')),
-          pages: new FileRef(path.join(__dirname, 'app/pages')),
-          app: new FileRef(path.join(__dirname, 'app/app')),
-          'next.config.js': new FileRef(
-            path.join(__dirname, 'app/next.config.js')
-          ),
-        },
+        files: new FileRef(path.join(__dirname, 'app')),
         dependencies: {
           react: 'experimental',
           'react-dom': 'experimental',

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

@@ -0,0 +1,57 @@
+import { createNext, FileRef } from 'e2e-utils'
+import { NextInstance } from 'test/lib/next-modes/base'
+import { waitFor } from 'next-test-utils'
+import path from 'path'
+import webdriver from 'next-webdriver'
+
+describe('app dir prefetching', () => {
+  if ((global as any).isNextDeploy) {
+    it('should skip next deploy for now', () => {})
+    return
+  }
+
+  if (process.env.NEXT_TEST_REACT_VERSION === '^17') {
+    it('should skip for react v17', () => {})
+    return
+  }
+  let next: NextInstance
+
+  beforeAll(async () => {
+    next = await createNext({
+      files: new FileRef(path.join(__dirname, 'app-prefetch')),
+      dependencies: {
+        react: 'experimental',
+        'react-dom': 'experimental',
+      },
+      skipStart: true,
+    })
+    await next.start()
+  })
+  afterAll(() => next.destroy())
+
+  it('should show layout eagerly when prefetched with loading one level down', async () => {
+    const browser = await webdriver(next.url, '/')
+    // Ensure the page is prefetched
+    await waitFor(1000)
+
+    const before = Date.now()
+    await browser
+      .elementByCss('#to-dashboard')
+      .click()
+      .waitForElementByCss('#dashboard-layout')
+    const after = Date.now()
+    const timeToComplete = after - before
+
+    expect(timeToComplete < 1000).toBe(true)
+
+    expect(await browser.elementByCss('#dashboard-layout').text()).toBe(
+      'Dashboard Hello World'
+    )
+
+    await browser.waitForElementByCss('#dashboard-page')
+
+    expect(await browser.waitForElementByCss('#dashboard-page').text()).toBe(
+      'Welcome to the dashboard'
+    )
+  })
+})

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

@@ -20,12 +20,7 @@ describe('app dir rendering', () => {
 
   beforeAll(async () => {
     next = await createNext({
-      files: {
-        app: new FileRef(path.join(__dirname, 'app-rendering/app')),
-        'next.config.js': new FileRef(
-          path.join(__dirname, 'app-rendering/next.config.js')
-        ),
-      },
+      files: new FileRef(path.join(__dirname, 'app-rendering')),
       dependencies: {
         react: 'experimental',
         'react-dom': 'experimental',

test/e2e/app-dir/rsc-basic.test.ts

@@ -35,15 +35,8 @@ describe('app dir - react server components', () => {
   }
 
   beforeAll(async () => {
-    const appDir = path.join(__dirname, './rsc-basic')
     next = await createNext({
-      files: {
-        node_modules_bak: new FileRef(path.join(appDir, 'node_modules_bak')),
-        public: new FileRef(path.join(appDir, 'public')),
-        components: new FileRef(path.join(appDir, 'components')),
-        app: new FileRef(path.join(appDir, 'app')),
-        'next.config.js': new FileRef(path.join(appDir, 'next.config.js')),
-      },
+      files: new FileRef(path.join(__dirname, './rsc-basic')),
       dependencies: {
         'styled-components': '6.0.0-alpha.5',
         react: 'experimental',

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

@@ -0,0 +1,66 @@
+import { createNext, FileRef } from 'e2e-utils'
+import { NextInstance } from 'test/lib/next-modes/base'
+import { fetchViaHTTP, renderViaHTTP } from 'next-test-utils'
+import path from 'path'
+import cheerio from 'cheerio'
+import webdriver from 'next-webdriver'
+
+describe('app-dir trailingSlash handling', () => {
+  if ((global as any).isNextDeploy) {
+    it('should skip next deploy for now', () => {})
+    return
+  }
+
+  if (process.env.NEXT_TEST_REACT_VERSION === '^17') {
+    it('should skip for react v17', () => {})
+    return
+  }
+  let next: NextInstance
+
+  beforeAll(async () => {
+    next = await createNext({
+      files: new FileRef(path.join(__dirname, 'trailingslash')),
+      dependencies: {
+        react: 'experimental',
+        'react-dom': 'experimental',
+      },
+      skipStart: true,
+    })
+
+    await next.start()
+  })
+  afterAll(() => next.destroy())
+
+  it('should redirect route when requesting it directly', async () => {
+    const res = await fetchViaHTTP(
+      next.url,
+      '/a',
+      {},
+      {
+        redirect: 'manual',
+      }
+    )
+    expect(res.status).toBe(308)
+    expect(res.headers.get('location')).toBe(next.url + '/a/')
+  })
+
+  it('should render link with trailing slash', async () => {
+    const html = await renderViaHTTP(next.url, '/')
+    const $ = cheerio.load(html)
+    expect($('#to-a-trailing-slash').attr('href')).toBe('/a/')
+  })
+
+  it('should redirect route when requesting it directly by browser', async () => {
+    const browser = await webdriver(next.url, '/a')
+    expect(await browser.waitForElementByCss('#a-page').text()).toBe('A page')
+  })
+
+  it('should redirect route when clicking link', async () => {
+    const browser = await webdriver(next.url, '/')
+    await browser
+      .elementByCss('#to-a-trailing-slash')
+      .click()
+      .waitForElementByCss('#a-page')
+    expect(await browser.waitForElementByCss('#a-page').text()).toBe('A page')
+  })
+})

test/e2e/app-dir/trailingslash/app/a/page.server.js

@@ -0,0 +1,9 @@
+import Link from 'next/link'
+export default function HomePage() {
+  return (
+    <>
+      <h1 id="a-page">A page</h1>
+      <Link href="/">To home</Link>
+    </>
+  )
+}

test/e2e/app-dir/trailingslash/app/layout.server.js

@@ -0,0 +1,10 @@
+export default function Root({ children }) {
+  return (
+    <html>
+      <head>
+        <title>Hello</title>
+      </head>
+      <body>{children}</body>
+    </html>
+  )
+}

test/e2e/app-dir/trailingslash/app/page.server.js

@@ -0,0 +1,12 @@
+import Link from 'next/link'
+export default function HomePage() {
+  return (
+    <>
+      <p>
+        <Link href="/a/">
+          <a id="to-a-trailing-slash">To a with trailing slash</a>
+        </Link>
+      </p>
+    </>
+  )
+}

test/e2e/app-dir/trailingslash/next.config.js

@@ -0,0 +1,9 @@
+module.exports = {
+  experimental: {
+    appDir: true,
+    serverComponents: true,
+    legacyBrowsers: false,
+    browsersListForSwc: true,
+  },
+  trailingSlash: true,
+}