test(nextjs): Add UI components for cached/dynamic content (#24874)

Adds UI components and an index page so it's easier to know what's
happening on each page when manually using the E2E tests.

Example:

<img width="798" height="334" alt="image"
src="https://github.com/user-attachments/assets/1f5027f8-8602-4b10-be75-441cb781f78c"
/>

Author: s1gr1d

dev-packages/e2e-tests/test-applications/nextjs-16-cacheComponents/app/(cached-nesting)/cached-mid-layout/[id]/layout.tsx

@@ -1,5 +1,6 @@
 import type { ReactNode } from 'react';
 import { cacheLife } from 'next/cache';
+import { CachedBox } from '@/components/scenarioBox';
 
 // The awaited param puts the request id into the cache key, so a fresh id is a guaranteed miss
 // and the entry cannot come from a build-time fill. `children` passes through as an uncached hole.
@@ -15,11 +16,14 @@ export default async function CachedMidLayout({
   const { id } = await params;
   await new Promise(resolve => setTimeout(resolve, 100));
   return (
-    <div data-testid="cached-mid-layout">
-      <p id="cached-layout-stamp">
-        {id}:{Date.now()}
-      </p>
-      {children}
-    </div>
+    <main>
+      <h1>Cached layout, dynamic page</h1>
+      <CachedBox label="CachedMidLayout · use cache · hours · keyed by [id]">
+        <p id="cached-layout-stamp">
+          {id}:{Date.now()}
+        </p>
+        {children}
+      </CachedBox>
+    </main>
   );
 }

dev-packages/e2e-tests/test-applications/nextjs-16-cacheComponents/app/(cached-nesting)/cached-mid-layout/[id]/page.tsx

@@ -1,6 +1,11 @@
 import { headers } from 'next/headers';
+import { DynamicBox } from '@/components/scenarioBox';
 
 export default async function Page() {
   await headers();
-  return <p id="dynamic-leaf">Dynamic leaf: {Date.now()}</p>;
+  return (
+    <DynamicBox label="page · awaits headers">
+      <p id="dynamic-leaf">Dynamic leaf: {Date.now()}</p>
+    </DynamicBox>
+  );
 }

dev-packages/e2e-tests/test-applications/nextjs-16-cacheComponents/app/(cached-nesting)/dynamic-layouts/[id]/layout-cached-leaf/page.tsx

@@ -1,13 +1,16 @@
 import { cacheLife } from 'next/cache';
+import { CachedBox } from '@/components/scenarioBox';
 
 async function CachedLeaf({ id }: { id: string }) {
   'use cache';
   cacheLife('hours');
   await new Promise(resolve => setTimeout(resolve, 100));
   return (
-    <p id="cached-leaf">
-      {id}:{Date.now()}
-    </p>
+    <CachedBox label="CachedLeaf · use cache · hours">
+      <p id="cached-leaf">
+        {id}:{Date.now()}
+      </p>
+    </CachedBox>
   );
 }
 

dev-packages/e2e-tests/test-applications/nextjs-16-cacheComponents/app/(cached-nesting)/dynamic-layouts/[id]/layout.tsx

@@ -1,7 +1,16 @@
 import type { ReactNode } from 'react';
 import { headers } from 'next/headers';
+import { DynamicBox } from '@/components/scenarioBox';
 
 export default async function DynamicLayout({ children }: { children: ReactNode }) {
   await headers();
-  return <div data-testid="dynamic-layout">{children}</div>;
+  return (
+    <main>
+      <h1>Dynamic layout, cached leaf</h1>
+      <DynamicBox label="DynamicLayout · awaits headers">
+        <p>request-time: {Date.now()}</p>
+        {children}
+      </DynamicBox>
+    </main>
+  );
 }

dev-packages/e2e-tests/test-applications/nextjs-16-cacheComponents/app/(cached-nesting)/mixed-lifetimes/[id]/layout.tsx

@@ -1,5 +1,6 @@
 import type { ReactNode } from 'react';
 import { cacheLife } from 'next/cache';
+import { CachedBox } from '@/components/scenarioBox';
 
 // Hard-expires after 2s while the page's cached component lives for hours, so one request can
 // refill the layout while hitting the component: two cached levels with different origin traces.
@@ -14,11 +15,14 @@ export default async function ShortLivedLayout({
   cacheLife({ revalidate: 1, expire: 2 });
   const { id } = await params;
   return (
-    <div data-testid="short-lived-layout">
-      <p id="layout-stamp">
-        {id}:{Date.now()}
-      </p>
-      {children}
-    </div>
+    <main>
+      <h1>Mixed lifetimes</h1>
+      <CachedBox label="ShortLivedLayout · use cache · expires after 2s · keyed by [id]">
+        <p id="layout-stamp">
+          {id}:{Date.now()}
+        </p>
+        {children}
+      </CachedBox>
+    </main>
   );
 }

dev-packages/e2e-tests/test-applications/nextjs-16-cacheComponents/app/(cached-nesting)/mixed-lifetimes/[id]/page.tsx

@@ -1,19 +1,27 @@
 import { headers } from 'next/headers';
 import { cacheLife } from 'next/cache';
+import { CachedBox, DynamicBox } from '@/components/scenarioBox';
 
 async function LongLivedComponent({ id }: { id: string }) {
   'use cache';
   cacheLife('hours');
   await new Promise(resolve => setTimeout(resolve, 100));
   return (
-    <p id="component-stamp">
-      {id}:{Date.now()}
-    </p>
+    <CachedBox label="LongLivedComponent · use cache · hours">
+      <p id="component-stamp">
+        {id}:{Date.now()}
+      </p>
+    </CachedBox>
   );
 }
 
 export default async function Page({ params }: { params: Promise<{ id: string }> }) {
   const { id } = await params;
   await headers();
-  return <LongLivedComponent id={id} />;
+  return (
+    <DynamicBox label="page · awaits headers">
+      <p>request-time: {Date.now()}</p>
+      <LongLivedComponent id={id} />
+    </DynamicBox>
+  );
 }

dev-packages/e2e-tests/test-applications/nextjs-16-cacheComponents/app/(cached-nesting)/shared-layout/[id]/a/page.tsx

@@ -1,6 +1,11 @@
 import { headers } from 'next/headers';
+import { DynamicBox } from '@/components/scenarioBox';
 
 export default async function Page() {
   await headers();
-  return <p id="route-a">Route a: {Date.now()}</p>;
+  return (
+    <DynamicBox label="route a · awaits headers">
+      <p id="route-a">Route a: {Date.now()}</p>
+    </DynamicBox>
+  );
 }

dev-packages/e2e-tests/test-applications/nextjs-16-cacheComponents/app/(cached-nesting)/shared-layout/[id]/b/page.tsx

@@ -1,6 +1,11 @@
 import { headers } from 'next/headers';
+import { DynamicBox } from '@/components/scenarioBox';
 
 export default async function Page() {
   await headers();
-  return <p id="route-b">Route b: {Date.now()}</p>;
+  return (
+    <DynamicBox label="route b · awaits headers">
+      <p id="route-b">Route b: {Date.now()}</p>
+    </DynamicBox>
+  );
 }

dev-packages/e2e-tests/test-applications/nextjs-16-cacheComponents/app/(cached-nesting)/shared-layout/[id]/layout.tsx

@@ -1,5 +1,6 @@
 import type { ReactNode } from 'react';
 import { cacheLife } from 'next/cache';
+import { CachedBox } from '@/components/scenarioBox';
 
 // One cache entry (keyed by id) shared by the sibling routes `a` and `b` below.
 export default async function SharedLayout({
@@ -14,11 +15,14 @@ export default async function SharedLayout({
   const { id } = await params;
   await new Promise(resolve => setTimeout(resolve, 100));
   return (
-    <div data-testid="shared-layout">
-      <p id="shared-layout-stamp">
-        {id}:{Date.now()}
-      </p>
-      {children}
-    </div>
+    <main>
+      <h1>Shared layout across sibling routes</h1>
+      <CachedBox label="SharedLayout · use cache · hours · shared by /a and /b">
+        <p id="shared-layout-stamp">
+          {id}:{Date.now()}
+        </p>
+        {children}
+      </CachedBox>
+    </main>
   );
 }

dev-packages/e2e-tests/test-applications/nextjs-16-cacheComponents/app/cached-sibling-components/page.tsx

@@ -1,14 +1,17 @@
 import { Suspense } from 'react';
 import { cacheLife } from 'next/cache';
+import { CachedBox, DynamicBox } from '@/components/scenarioBox';
 
 async function CachedSection({ id, label }: { id: string; label: string }) {
   'use cache';
   cacheLife('hours');
   await new Promise(resolve => setTimeout(resolve, 100));
   return (
-    <section id={`cached-${label}`}>
-      {label}:{id}:{Date.now()}
-    </section>
+    <CachedBox label={`CachedSection "${label}" · use cache · hours`}>
+      <section id={`cached-${label}`}>
+        {label}:{id}:{Date.now()}
+      </section>
+    </CachedBox>
   );
 }
 
@@ -18,17 +21,21 @@ async function DynamicContent({ searchParams }: { searchParams: Promise<{ id?: s
   // separate entries (the props are part of the cache key).
   const { id = 'default-id' } = await searchParams;
   return (
-    <>
+    <DynamicBox label="dynamic hole · awaits searchParams">
+      <p>request-time: {Date.now()}</p>
       <CachedSection id={id} label="first" />
       <CachedSection id={id} label="second" />
-    </>
+    </DynamicBox>
   );
 }
 
 export default function Page({ searchParams }: { searchParams: Promise<{ id?: string }> }) {
   return (
-    <Suspense fallback={<div>Loading...</div>}>
-      <DynamicContent searchParams={searchParams} />
-    </Suspense>
+    <main>
+      <h1>Cached sibling components</h1>
+      <Suspense fallback={<div>Loading...</div>}>
+        <DynamicContent searchParams={searchParams} />
+      </Suspense>
+    </main>
   );
 }