diff --git a/packages/astro/test/astro-response.test.js b/packages/astro/test/astro-response.test.js
deleted file mode 100644
index 2440c7362b22..000000000000
--- a/packages/astro/test/astro-response.test.js
+++ /dev/null
@@ -1,45 +0,0 @@
-// @ts-check
-import assert from 'node:assert/strict';
-import { after, before, describe, it } from 'node:test';
-import { loadFixture } from './test-utils.js';
-
-// Asset bundling
-describe('Returning responses', () => {
-	/** @type {Awaited<ReturnType<typeof loadFixture>>} */
-	let fixture;
-	/** @type {import('./test-utils').DevServer} */
-	let devServer;
-
-	before(async () => {
-		fixture = await loadFixture({
-			root: './fixtures/astro-response/',
-		});
-
-		devServer = await fixture.startDevServer();
-	});
-
-	after(async () => {
-		await devServer.stop();
-	});
-
-	it('Works from a page', async () => {
-		const response = await fixture.fetch('/not-found');
-		assert.equal(response.status, 404);
-	});
-
-	it('Returns the default 404 is body is null', async () => {
-		const response = await fixture.fetch('/not-found');
-		const html = await response.text();
-
-		assert.equal(response.status, 404);
-		assert.equal(html.includes('<pre>Path: /not-found</pre>'), true);
-	});
-
-	it('Returns the page is body is not null', async () => {
-		const response = await fixture.fetch('/not-found-custom');
-		const html = await response.text();
-
-		assert.equal(response.status, 404);
-		assert.equal(html.includes('Custom 404'), true);
-	});
-});
diff --git a/packages/astro/test/fixtures/astro-response/package.json b/packages/astro/test/fixtures/astro-response/package.json
deleted file mode 100644
index a832534901e2..000000000000
--- a/packages/astro/test/fixtures/astro-response/package.json
+++ /dev/null
@@ -1,8 +0,0 @@
-{
-  "name": "@test/astro-response",
-  "version": "0.0.0",
-  "private": true,
-  "dependencies": {
-    "astro": "workspace:*"
-  }
-}
diff --git a/packages/astro/test/fixtures/astro-response/src/pages/not-found-custom.astro b/packages/astro/test/fixtures/astro-response/src/pages/not-found-custom.astro
deleted file mode 100644
index 482331ebc5da..000000000000
--- a/packages/astro/test/fixtures/astro-response/src/pages/not-found-custom.astro
+++ /dev/null
@@ -1,4 +0,0 @@
----
-Astro.response.status = 404
----
-<div>Custom 404</div>
\ No newline at end of file
diff --git a/packages/astro/test/fixtures/astro-response/src/pages/not-found.astro b/packages/astro/test/fixtures/astro-response/src/pages/not-found.astro
deleted file mode 100644
index dd339e72b775..000000000000
--- a/packages/astro/test/fixtures/astro-response/src/pages/not-found.astro
+++ /dev/null
@@ -1,6 +0,0 @@
----
-return new Response(null, {
-	status: 404,
-	statusText: `Not found`
-});
----
diff --git a/packages/astro/test/units/app/astro-response.test.js b/packages/astro/test/units/app/astro-response.test.js
new file mode 100644
index 000000000000..0e619bb9e937
--- /dev/null
+++ b/packages/astro/test/units/app/astro-response.test.js
@@ -0,0 +1,98 @@
+// @ts-check
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { App } from '../../../dist/core/app/app.js';
+import { createComponent, render } from '../../../dist/runtime/server/index.js';
+import { createManifest, createRouteInfo } from './test-helpers.js';
+
+const notFoundRouteData = {
+	route: '/not-found',
+	component: 'src/pages/not-found.astro',
+	params: [],
+	pathname: '/not-found',
+	distURL: [],
+	pattern: /^\/not-found\/?$/,
+	segments: [[{ content: 'not-found', dynamic: false, spread: false }]],
+	type: 'page',
+	prerender: false,
+	fallbackRoutes: [],
+	isIndex: false,
+	origin: 'project',
+};
+
+const notFoundCustomRouteData = {
+	route: '/not-found-custom',
+	component: 'src/pages/not-found-custom.astro',
+	params: [],
+	pathname: '/not-found-custom',
+	distURL: [],
+	pattern: /^\/not-found-custom\/?$/,
+	segments: [[{ content: 'not-found-custom', dynamic: false, spread: false }]],
+	type: 'page',
+	prerender: false,
+	fallbackRoutes: [],
+	isIndex: false,
+	origin: 'project',
+};
+
+const notFoundPage = createComponent(() => {
+	return new Response(null, {
+		status: 404,
+		statusText: 'Not found',
+	});
+});
+
+const notFoundCustomPage = createComponent((result, props, slots) => {
+	const Astro = result.createAstro(props, slots);
+	Astro.response.status = 404;
+	return render`<div>Custom 404</div>`;
+});
+
+const pageMap = new Map([
+	[
+		notFoundRouteData.component,
+		async () => ({
+			page: async () => ({
+				default: notFoundPage,
+			}),
+		}),
+	],
+	[
+		notFoundCustomRouteData.component,
+		async () => ({
+			page: async () => ({
+				default: notFoundCustomPage,
+			}),
+		}),
+	],
+]);
+
+const app = new App(
+	createManifest({
+		routes: [createRouteInfo(notFoundRouteData), createRouteInfo(notFoundCustomRouteData)],
+		pageMap,
+	}),
+);
+
+describe('Returning responses', () => {
+	it('Works from a page', async () => {
+		const response = await app.render(new Request('http://example.com/not-found'));
+		assert.equal(response.status, 404);
+	});
+
+	it('Returns the default 404 if body is null', async () => {
+		const response = await app.render(new Request('http://example.com/not-found'));
+		const html = await response.text();
+
+		assert.equal(response.status, 404);
+		assert.equal(html.includes('<pre>Path: /not-found</pre>'), true);
+	});
+
+	it('Returns the page if body is not null', async () => {
+		const response = await app.render(new Request('http://example.com/not-found-custom'));
+		const html = await response.text();
+
+		assert.equal(response.status, 404);
+		assert.equal(html.includes('Custom 404'), true);
+	});
+});
diff --git a/packages/astro/test/units/app/error-pages.test.js b/packages/astro/test/units/app/error-pages.test.js
index 352a7b83d8ff..325a1ba77562 100644
--- a/packages/astro/test/units/app/error-pages.test.js
+++ b/packages/astro/test/units/app/error-pages.test.js
@@ -3,60 +3,7 @@ import assert from 'node:assert/strict';
 import { describe, it } from 'node:test';
 import { App } from '../../../dist/core/app/app.js';
 import { createComponent, maybeRenderHead, render } from '../../../dist/runtime/server/index.js';
-
-function createManifest({ routes, pageMap, trailingSlash = 'ignore' }) {
-	const rootDir = new URL('file:///astro-test/');
-	const buildDir = new URL('file:///astro-test/dist/');
-
-	return {
-		adapterName: 'test-adapter',
-		routes,
-		site: undefined,
-		base: '/',
-		userAssetsBase: undefined,
-		trailingSlash,
-		buildFormat: 'directory',
-		compressHTML: false,
-		assetsPrefix: undefined,
-		renderers: [],
-		serverLike: true,
-		clientDirectives: new Map(),
-		entryModules: {},
-		inlinedScripts: new Map(),
-		assets: new Set(),
-		componentMetadata: new Map(),
-		pageModule: undefined,
-		pageMap,
-		serverIslandMappings: undefined,
-		key: Promise.resolve(/** @type {CryptoKey} */ ({})),
-		i18n: undefined,
-		middleware: undefined,
-		actions: undefined,
-		sessionDriver: undefined,
-		checkOrigin: false,
-		allowedDomains: undefined,
-		sessionConfig: undefined,
-		cacheDir: rootDir,
-		srcDir: rootDir,
-		outDir: buildDir,
-		rootDir,
-		publicDir: rootDir,
-		assetsDir: 'assets',
-		buildClientDir: buildDir,
-		buildServerDir: buildDir,
-		csp: undefined,
-		image: {},
-		shouldInjectCspMetaTags: false,
-		devToolbar: {
-			enabled: false,
-			latestAstroVersion: undefined,
-			debugInfoOutput: undefined,
-			placement: undefined,
-		},
-		internalFetchHeaders: undefined,
-		logLevel: 'silent',
-	};
-}
+import { createManifest } from './test-helpers.js';
 
 describe('App render error pages', () => {
 	it('preserves headers and body for 500 responses from routes', async () => {
diff --git a/packages/astro/test/units/app/locals.test.js b/packages/astro/test/units/app/locals.test.js
index c5aa18655410..907b4ac74d0b 100644
--- a/packages/astro/test/units/app/locals.test.js
+++ b/packages/astro/test/units/app/locals.test.js
@@ -2,60 +2,7 @@ import assert from 'node:assert/strict';
 import { describe, it } from 'node:test';
 import { App } from '../../../dist/core/app/app.js';
 import { createComponent, render } from '../../../dist/runtime/server/index.js';
-
-function createManifest({ routes, pageMap }) {
-	const rootDir = new URL('file:///astro-test/');
-	const buildDir = new URL('file:///astro-test/dist/');
-
-	return {
-		adapterName: 'test-adapter',
-		routes,
-		site: undefined,
-		base: '/',
-		userAssetsBase: undefined,
-		trailingSlash: 'ignore',
-		buildFormat: 'directory',
-		compressHTML: false,
-		assetsPrefix: undefined,
-		renderers: [],
-		serverLike: true,
-		clientDirectives: new Map(),
-		entryModules: {},
-		inlinedScripts: new Map(),
-		assets: new Set(),
-		componentMetadata: new Map(),
-		pageModule: undefined,
-		pageMap,
-		serverIslandMappings: undefined,
-		key: Promise.resolve(/** @type {CryptoKey} */ ({})),
-		i18n: undefined,
-		middleware: undefined,
-		actions: undefined,
-		sessionDriver: undefined,
-		checkOrigin: false,
-		allowedDomains: undefined,
-		sessionConfig: undefined,
-		cacheDir: rootDir,
-		srcDir: rootDir,
-		outDir: buildDir,
-		rootDir,
-		publicDir: rootDir,
-		assetsDir: 'assets',
-		buildClientDir: buildDir,
-		buildServerDir: buildDir,
-		csp: undefined,
-		image: {},
-		shouldInjectCspMetaTags: false,
-		devToolbar: {
-			enabled: false,
-			latestAstroVersion: undefined,
-			debugInfoOutput: undefined,
-			placement: undefined,
-		},
-		internalFetchHeaders: undefined,
-		logLevel: 'silent',
-	};
-}
+import { createManifest } from './test-helpers.js';
 
 const fooRouteData = {
 	route: '/foo',
diff --git a/packages/astro/test/units/app/response.test.js b/packages/astro/test/units/app/response.test.js
index 2b289e634d77..ad46d52090d3 100644
--- a/packages/astro/test/units/app/response.test.js
+++ b/packages/astro/test/units/app/response.test.js
@@ -2,60 +2,7 @@ import assert from 'node:assert/strict';
 import { describe, it } from 'node:test';
 import { App } from '../../../dist/core/app/app.js';
 import { createComponent, render } from '../../../dist/runtime/server/index.js';
-
-function createManifest({ routes, pageMap }) {
-	const rootDir = new URL('file:///astro-test/');
-	const buildDir = new URL('file:///astro-test/dist/');
-
-	return {
-		adapterName: 'test-adapter',
-		routes,
-		site: undefined,
-		base: '/',
-		userAssetsBase: undefined,
-		trailingSlash: 'ignore',
-		buildFormat: 'directory',
-		compressHTML: false,
-		assetsPrefix: undefined,
-		renderers: [],
-		serverLike: true,
-		clientDirectives: new Map(),
-		entryModules: {},
-		inlinedScripts: new Map(),
-		assets: new Set(),
-		componentMetadata: new Map(),
-		pageModule: undefined,
-		pageMap,
-		serverIslandMappings: undefined,
-		key: Promise.resolve(/** @type {CryptoKey} */ ({})),
-		i18n: undefined,
-		middleware: undefined,
-		actions: undefined,
-		sessionDriver: undefined,
-		checkOrigin: false,
-		allowedDomains: undefined,
-		sessionConfig: undefined,
-		cacheDir: rootDir,
-		srcDir: rootDir,
-		outDir: buildDir,
-		rootDir,
-		publicDir: rootDir,
-		assetsDir: 'assets',
-		buildClientDir: buildDir,
-		buildServerDir: buildDir,
-		csp: undefined,
-		image: {},
-		shouldInjectCspMetaTags: false,
-		devToolbar: {
-			enabled: false,
-			latestAstroVersion: undefined,
-			debugInfoOutput: undefined,
-			placement: undefined,
-		},
-		internalFetchHeaders: undefined,
-		logLevel: 'silent',
-	};
-}
+import { createManifest } from './test-helpers.js';
 
 const statusRouteData = {
 	route: '/status-code',
diff --git a/packages/astro/test/units/app/test-helpers.js b/packages/astro/test/units/app/test-helpers.js
new file mode 100644
index 000000000000..d76a79d47b6a
--- /dev/null
+++ b/packages/astro/test/units/app/test-helpers.js
@@ -0,0 +1,65 @@
+// @ts-check
+
+export function createManifest({ routes, pageMap, base = '/', trailingSlash = 'ignore' } = {}) {
+	const rootDir = new URL('file:///astro-test/');
+	const buildDir = new URL('file:///astro-test/dist/');
+
+	return {
+		adapterName: 'test-adapter',
+		routes,
+		site: undefined,
+		base,
+		userAssetsBase: undefined,
+		trailingSlash: /** @type {'always' | 'never' | 'ignore'} */ (trailingSlash),
+		buildFormat: /** @type {'directory'} */ ('directory'),
+		compressHTML: false,
+		assetsPrefix: undefined,
+		renderers: [],
+		serverLike: true,
+		clientDirectives: new Map(),
+		entryModules: {},
+		inlinedScripts: new Map(),
+		assets: new Set(),
+		componentMetadata: new Map(),
+		pageModule: undefined,
+		pageMap,
+		serverIslandMappings: undefined,
+		key: Promise.resolve(/** @type {CryptoKey} */ ({})),
+		i18n: undefined,
+		middleware: undefined,
+		actions: undefined,
+		sessionDriver: undefined,
+		checkOrigin: false,
+		allowedDomains: undefined,
+		sessionConfig: undefined,
+		cacheDir: rootDir,
+		srcDir: rootDir,
+		outDir: buildDir,
+		rootDir,
+		publicDir: rootDir,
+		assetsDir: 'assets',
+		buildClientDir: buildDir,
+		buildServerDir: buildDir,
+		csp: undefined,
+		image: {},
+		shouldInjectCspMetaTags: false,
+		devToolbar: {
+			enabled: false,
+			latestAstroVersion: undefined,
+			debugInfoOutput: undefined,
+			placement: undefined,
+		},
+		internalFetchHeaders: undefined,
+		logLevel: /** @type {'silent'} */ ('silent'),
+	};
+}
+
+export function createRouteInfo(routeData) {
+	return {
+		routeData,
+		file: routeData.component,
+		links: [],
+		scripts: [],
+		styles: [],
+	};
+}
diff --git a/packages/astro/test/units/app/trailing-slash.test.js b/packages/astro/test/units/app/trailing-slash.test.js
index 5f5b5f08bc09..063c228e1dc3 100644
--- a/packages/astro/test/units/app/trailing-slash.test.js
+++ b/packages/astro/test/units/app/trailing-slash.test.js
@@ -2,60 +2,7 @@ import assert from 'node:assert/strict';
 import { describe, it } from 'node:test';
 import { App } from '../../../dist/core/app/app.js';
 import { createComponent, render } from '../../../dist/runtime/server/index.js';
-
-function createManifest({ routes, pageMap, base = '/', trailingSlash = 'ignore' }) {
-	const rootDir = new URL('file:///astro-test/');
-	const buildDir = new URL('file:///astro-test/dist/');
-
-	return {
-		adapterName: 'test-adapter',
-		routes,
-		site: undefined,
-		base,
-		userAssetsBase: undefined,
-		trailingSlash,
-		buildFormat: 'directory',
-		compressHTML: false,
-		assetsPrefix: undefined,
-		renderers: [],
-		serverLike: true,
-		clientDirectives: new Map(),
-		entryModules: {},
-		inlinedScripts: new Map(),
-		assets: new Set(),
-		componentMetadata: new Map(),
-		pageModule: undefined,
-		pageMap,
-		serverIslandMappings: undefined,
-		key: Promise.resolve(/** @type {CryptoKey} */ ({})),
-		i18n: undefined,
-		middleware: undefined,
-		actions: undefined,
-		sessionDriver: undefined,
-		checkOrigin: false,
-		allowedDomains: undefined,
-		sessionConfig: undefined,
-		cacheDir: rootDir,
-		srcDir: rootDir,
-		outDir: buildDir,
-		rootDir,
-		publicDir: rootDir,
-		assetsDir: 'assets',
-		buildClientDir: buildDir,
-		buildServerDir: buildDir,
-		csp: undefined,
-		image: {},
-		shouldInjectCspMetaTags: false,
-		devToolbar: {
-			enabled: false,
-			latestAstroVersion: undefined,
-			debugInfoOutput: undefined,
-			placement: undefined,
-		},
-		internalFetchHeaders: undefined,
-		logLevel: 'silent',
-	};
-}
+import { createManifest } from './test-helpers.js';
 
 function escapeRoute(route) {
 	return route.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index f262bb3308db..d29f6b2cd4ba 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -2467,12 +2467,6 @@ importers:
         specifier: workspace:*
         version: link:../../..
 
-  packages/astro/test/fixtures/astro-response:
-    dependencies:
-      astro:
-        specifier: workspace:*
-        version: link:../../..
-
   packages/astro/test/fixtures/astro-scripts:
     dependencies:
       '@tailwindcss/vite':