Updates the dev server to handle multiple routes matching the same URL (#4087)

* updates the dev server to handle multiple routes matching the same URL

* Adding an error message when multiple routes match in SSR

* resetting the flag used by the `calledTwiceTest`

* injected routes should be sorted with a higher priority than user-defined routes

* adding routing priority tests for injected routes

* chore: add changeset

* adding a dev test to make sure getStaticPaths is called once

14 files changed, 397 insertions, 216 deletions

diff --git a/.changeset/gold-olives-cover.md b/.changeset/gold-olives-cover.md
new file mode 100644
index 000000000..783629343
--- /dev/null
+++ b/.changeset/gold-olives-cover.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes a couple routing bugs that could lead to routing differences in `dev` vs. `build` when using multiple dynamic routes
diff --git a/packages/astro/src/core/routing/index.ts b/packages/astro/src/core/routing/index.ts
index 84ec1f66e..13b23d78b 100644
--- a/packages/astro/src/core/routing/index.ts
+++ b/packages/astro/src/core/routing/index.ts
@@ -1,5 +1,5 @@
 export { createRouteManifest } from './manifest/create.js';
 export { deserializeRouteData, serializeRouteData } from './manifest/serialization.js';
-export { matchRoute } from './match.js';
+export { matchRoute, matchAllRoutes } from './match.js';
 export { getParams } from './params.js';
 export { validateGetStaticPathsModule, validateGetStaticPathsResult } from './validation.js';
diff --git a/packages/astro/src/core/routing/manifest/create.ts b/packages/astro/src/core/routing/manifest/create.ts
index ba40f3b1b..bb718dd45 100644
--- a/packages/astro/src/core/routing/manifest/create.ts
+++ b/packages/astro/src/core/routing/manifest/create.ts
@@ -1,4 +1,4 @@
-import type { AstroConfig, ManifestData, RouteData, RoutePart } from '../../../@types/astro';
+import type { AstroConfig, InjectedRoute, ManifestData, RouteData, RoutePart } from '../../../@types/astro';
 import type { LogOptions } from '../../logger/core';
 
 import fs from 'fs';
@@ -159,6 +159,29 @@ function comparator(a: Item, b: Item) {
 	return a.file < b.file ? -1 : 1;
 }
 
+function injectedRouteToItem(
+	{ config, cwd }: { config: AstroConfig; cwd?: string },
+	{ pattern, entryPoint }: InjectedRoute
+): Item {
+	const resolved = require.resolve(entryPoint, { paths: [cwd || fileURLToPath(config.root)] });
+
+	const ext = path.extname(pattern);
+
+	const type = resolved.endsWith('.astro') ? 'page' : 'endpoint';
+	const isPage = type === 'page';
+
+	return {
+		basename: pattern,
+		ext,
+		parts: getParts(pattern, resolved),
+		file: resolved,
+		isDir: false,
+		isIndex: true,
+		isPage,
+		routeSuffix: pattern.slice(pattern.indexOf('.'), -ext.length),
+	}
+}
+
 /** Create manifest of all static routes */
 export function createRouteManifest(
 	{ config, cwd }: { config: AstroConfig; cwd?: string },
@@ -288,7 +311,14 @@ export function createRouteManifest(
 		warn(logging, 'astro', `Missing pages directory: ${pagesDirRootRelative}`);
 	}
 
-	config?._ctx?.injectedRoutes?.forEach(({ pattern: name, entryPoint }) => {
+	config?._ctx?.injectedRoutes?.sort((a, b) =>
+		// sort injected routes in the same way as user-defined routes
+		comparator(
+			injectedRouteToItem({ config, cwd }, a),
+			injectedRouteToItem({ config, cwd}, b)
+		))
+		.reverse() // prepend to the routes array from lowest to highest priority
+		.forEach(({ pattern: name, entryPoint }) => {
 		const resolved = require.resolve(entryPoint, { paths: [cwd || fileURLToPath(config.root)] });
 		const component = slash(path.relative(cwd || fileURLToPath(config.root), resolved));
 
@@ -336,7 +366,10 @@ export function createRouteManifest(
 			);
 		}
 
-		routes.push({
+		// the routes array was already sorted by priority,
+		// pushing to the front of the list ensure that injected routes
+		// are given priority over all user-provided routes
+		routes.unshift({
 			type,
 			route,
 			pattern,
diff --git a/packages/astro/src/core/routing/match.ts b/packages/astro/src/core/routing/match.ts
index d2c2a8a54..bc4987926 100644
--- a/packages/astro/src/core/routing/match.ts
+++ b/packages/astro/src/core/routing/match.ts
@@ -4,3 +4,8 @@ import type { ManifestData, RouteData } from '../../@types/astro';
 export function matchRoute(pathname: string, manifest: ManifestData): RouteData | undefined {
 	return manifest.routes.find((route) => route.pattern.test(pathname));
 }
+
+/** Finds all matching routes from pathname */
+export function matchAllRoutes(pathname: string, manifest: ManifestData): RouteData[] {
+	return manifest.routes.filter((route) => route.pattern.test(pathname));
+}
diff --git a/packages/astro/src/vite-plugin-astro-server/index.ts b/packages/astro/src/vite-plugin-astro-server/index.ts
index 3449b7d3a..a77ca486d 100644
--- a/packages/astro/src/vite-plugin-astro-server/index.ts
+++ b/packages/astro/src/vite-plugin-astro-server/index.ts
@@ -19,7 +19,7 @@ import { getParamsAndProps, GetParamsAndPropsError } from '../core/render/core.j
 import { preload, ssr } from '../core/render/dev/index.js';
 import { RouteCache } from '../core/render/route-cache.js';
 import { createRequest } from '../core/request.js';
-import { createRouteManifest, matchRoute } from '../core/routing/index.js';
+import { createRouteManifest, matchAllRoutes, matchRoute } from '../core/routing/index.js';
 import { createSafeError, resolvePages } from '../core/util.js';
 import notFoundTemplate, { subpathNotUsedTemplate } from '../template/4xx.js';
 
@@ -248,26 +248,81 @@ async function handleRequest(
 		clientAddress: buildingToSSR ? req.socket.remoteAddress : undefined,
 	});
 
+	async function matchRoute() {
+		const matches = matchAllRoutes(pathname, manifest);
+
+		if (config.output === 'server' && matches.length > 1) {
+			throw new Error(`Found multiple matching routes for "${pathname}"! When using \`output: 'server'\`, only one route in \`src/pages\` can match a given URL. Found:
+
+${
+	matches.map(({ component }) => `- ${component}`).join('\n')
+}
+`);
+		}
+
+		for await (const maybeRoute of matches) {
+			const filePath = new URL(`./${maybeRoute.component}`, config.root);
+			const preloadedComponent = await preload({ astroConfig: config, filePath, viteServer });
+			const [, mod] = preloadedComponent;
+			// attempt to get static paths
+			// if this fails, we have a bad URL match!
+			const paramsAndPropsRes = await getParamsAndProps({
+				mod,
+				route: maybeRoute,
+				routeCache,
+				pathname: pathname,
+				logging,
+				ssr: config.output === 'server',
+			});
+
+			if (paramsAndPropsRes !== GetParamsAndPropsError.NoMatchingStaticPath) {
+				return {
+					route: maybeRoute,
+					filePath,
+					preloadedComponent,
+					mod,
+				}
+			}
+		}
+
+		if (matches.length) {
+			warn(
+				logging,
+				'getStaticPaths',
+				`Route pattern matched, but no matching static path found. (${pathname})`
+			);
+		}
+
+		log404(logging, pathname);
+		const custom404 = getCustom404Route(config, manifest);
+
+		if (custom404) {
+			const filePath = new URL(`./${custom404.component}`, config.root);
+			const preloadedComponent = await preload({ astroConfig: config, filePath, viteServer });
+			const [, mod] = preloadedComponent;
+				
+			return {
+				route: custom404,
+				filePath,
+				preloadedComponent,
+				mod
+			};
+		}
+
+		return undefined;
+	}
+
 	let filePath: URL | undefined;
 	try {
-		// Attempt to match the URL to a valid page route.
-		// If that fails, switch the response to a 404 response.
-		let route = matchRoute(pathname, manifest);
-		const statusCode = route ? 200 : 404;
+		const matchedRoute = await matchRoute();
 
-		if (!route) {
-			log404(logging, pathname);
-			const custom404 = getCustom404Route(config, manifest);
-			if (custom404) {
-				route = custom404;
-			} else {
-				return handle404Response(origin, config, req, res);
-			}
+		if (!matchedRoute) {
+			return handle404Response(origin, config, req, res);
 		}
 
-		filePath = new URL(`./${route.component}`, config.root);
-		const preloadedComponent = await preload({ astroConfig: config, filePath, viteServer });
-		const [, mod] = preloadedComponent;
+		const { route, preloadedComponent, mod } = matchedRoute;
+		filePath = matchedRoute.filePath;
+
 		// attempt to get static paths
 		// if this fails, we have a bad URL match!
 		const paramsAndPropsRes = await getParamsAndProps({
@@ -278,38 +333,6 @@ async function handleRequest(
 			logging,
 			ssr: config.output === 'server',
 		});
-		if (paramsAndPropsRes === GetParamsAndPropsError.NoMatchingStaticPath) {
-			warn(
-				logging,
-				'getStaticPaths',
-				`Route pattern matched, but no matching static path found. (${pathname})`
-			);
-			log404(logging, pathname);
-			const routeCustom404 = getCustom404Route(config, manifest);
-			if (routeCustom404) {
-				const filePathCustom404 = new URL(`./${routeCustom404.component}`, config.root);
-				const preloadedCompCustom404 = await preload({
-					astroConfig: config,
-					filePath: filePathCustom404,
-					viteServer,
-				});
-				const result = await ssr(preloadedCompCustom404, {
-					astroConfig: config,
-					filePath: filePathCustom404,
-					logging,
-					mode: 'development',
-					origin,
-					pathname: pathname,
-					request,
-					route: routeCustom404,
-					routeCache,
-					viteServer,
-				});
-				return await writeSSRResult(result, res);
-			} else {
-				return handle404Response(origin, config, req, res);
-			}
-		}
 
 		const options: SSROptions = {
 			astroConfig: config,
diff --git a/packages/astro/test/astro-get-static-paths.test.js b/packages/astro/test/astro-get-static-paths.test.js
index ffb3660d9..6d98446a1 100644
--- a/packages/astro/test/astro-get-static-paths.test.js
+++ b/packages/astro/test/astro-get-static-paths.test.js
@@ -4,6 +4,9 @@ import * as cheerio from 'cheerio';
 
 describe('getStaticPaths - build calls', () => {
 	before(async () => {
+		// reset the flag used by [...calledTwiceTest].astro between each test
+		globalThis.isCalledOnce = false;
+
 		const fixture = await loadFixture({
 			root: './fixtures/astro-get-static-paths/',
 			site: 'https://mysite.dev/',
@@ -11,17 +14,49 @@ describe('getStaticPaths - build calls', () => {
 		});
 		await fixture.build();
 	});
+
 	it('is only called once during build', () => {
 		// useless expect; if build() throws in setup then this test fails
 		expect(true).to.equal(true);
 	});
 });
 
+describe('getStaticPaths - dev calls', () => {
+	let fixture;
+	let devServer;
+
+	before(async () => {
+		// reset the flag used by [...calledTwiceTest].astro between each test
+		globalThis.isCalledOnce = false;
+		
+		fixture = await loadFixture({ root: './fixtures/astro-get-static-paths/' });
+		devServer = await fixture.startDevServer();
+	});
+
+	after(async () => {
+		devServer.stop();
+	});
+
+	it('only calls getStaticPaths once', async () => {
+		let res = await fixture.fetch('/a');
+		expect(res.status).to.equal(200);
+
+		res = await fixture.fetch('/b');
+		expect(res.status).to.equal(200);
+		
+		res = await fixture.fetch('/c');
+		expect(res.status).to.equal(200);
+	});
+});
+
 describe('getStaticPaths - 404 behavior', () => {
 	let fixture;
 	let devServer;
 
 	before(async () => {
+		// reset the flag used by [...calledTwiceTest].astro between each test
+		globalThis.isCalledOnce = false;
+		
 		fixture = await loadFixture({ root: './fixtures/astro-get-static-paths/' });
 		devServer = await fixture.startDevServer();
 	});
@@ -55,6 +90,9 @@ describe('getStaticPaths - route params type validation', () => {
 	let fixture, devServer;
 
 	before(async () => {
+		// reset the flag used by [...calledTwiceTest].astro between each test
+		globalThis.isCalledOnce = false;
+
 		fixture = await loadFixture({ root: './fixtures/astro-get-static-paths/' });
 		devServer = await fixture.startDevServer();
 	});
@@ -81,6 +119,9 @@ describe('getStaticPaths - numeric route params', () => {
 	let devServer;
 
 	before(async () => {
+		// reset the flag used by [...calledTwiceTest].astro between each test
+		globalThis.isCalledOnce = false;
+		
 		fixture = await loadFixture({
 			root: './fixtures/astro-get-static-paths/',
 			site: 'https://mysite.dev/',
diff --git a/packages/astro/test/fixtures/routing-priority/astro.config.mjs b/packages/astro/test/fixtures/routing-priority/astro.config.mjs
index 882e6515a..a5103a7f4 100644
--- a/packages/astro/test/fixtures/routing-priority/astro.config.mjs
+++ b/packages/astro/test/fixtures/routing-priority/astro.config.mjs
@@ -1,4 +1,7 @@
 import { defineConfig } from 'astro/config';
+import integration from './integration.mjs';
 
 // https://astro.build/config
-export default defineConfig({});
+export default defineConfig({
+	integrations: [integration()]
+});
diff --git a/packages/astro/test/fixtures/routing-priority/integration.mjs b/packages/astro/test/fixtures/routing-priority/integration.mjs
new file mode 100644
index 000000000..213812790
--- /dev/null
+++ b/packages/astro/test/fixtures/routing-priority/integration.mjs
@@ -0,0 +1,21 @@
+export default function() {
+	return {
+		name: '@astrojs/test-integration',
+			hooks: {
+				'astro:config:setup': ({ injectRoute }) => {
+					injectRoute({
+						pattern: '/injected',
+						entryPoint: './src/to-inject.astro'
+					});
+					injectRoute({
+						pattern: '/_injected',
+						entryPoint: './src/_to-inject.astro'
+					});
+					injectRoute({
+						pattern: '/[id]',
+						entryPoint: './src/[id].astro'
+					});
+				}
+			}
+	}
+}
diff --git a/packages/astro/test/fixtures/routing-priority/src/[id].astro b/packages/astro/test/fixtures/routing-priority/src/[id].astro
new file mode 100644
index 000000000..af235c9a8
--- /dev/null
+++ b/packages/astro/test/fixtures/routing-priority/src/[id].astro
@@ -0,0 +1,21 @@
+---
+export async function getStaticPaths() {
+	return [
+		{ params: { id: 'injected-1' } },
+		{ params: { id: 'injected-2' } }
+	];
+}
+
+const { id } = Astro.params;
+---
+<html lang="en">
+	<head>
+		<meta charset="utf-8" />
+		<meta name="viewport" content="width=device-width" />
+		<title>Routing</title>
+	</head>
+	<body>
+		<h1>[id].astro</h1>
+		<p>{id}</p>
+	</body>
+</html>
diff --git a/packages/astro/test/fixtures/routing-priority/src/_to-inject.astro b/packages/astro/test/fixtures/routing-priority/src/_to-inject.astro
new file mode 100644
index 000000000..4c5b6428f
--- /dev/null
+++ b/packages/astro/test/fixtures/routing-priority/src/_to-inject.astro
@@ -0,0 +1,12 @@
+---
+---
+<html lang="en">
+	<head>
+		<meta charset="utf-8" />
+		<meta name="viewport" content="width=device-width" />
+		<title>Routing</title>
+	</head>
+	<body>
+		<h1>to-inject.astro</h1>
+	</body>
+</html>
diff --git a/packages/astro/test/fixtures/routing-priority/src/pages/[page].astro b/packages/astro/test/fixtures/routing-priority/src/pages/[page].astro
new file mode 100644
index 000000000..7543bce3a
--- /dev/null
+++ b/packages/astro/test/fixtures/routing-priority/src/pages/[page].astro
@@ -0,0 +1,27 @@
+---
+	export async function getStaticPaths() {
+		return [
+			{
+				params: { page: "page-1" }
+			},
+			{
+				params: { page: "page-2" }
+			}
+		]
+	}
+---
+
+<html lang="en">
+
+<head>
+	<meta charset="utf-8" />
+	<meta name="viewport" content="width=device-width" />
+	<title>Routing</title>
+</head>
+
+<body>
+	<h1>[page].astro</h1>
+	<p>{Astro.params.page}</p>
+</body>
+
+</html>
diff --git a/packages/astro/test/fixtures/routing-priority/src/pages/[slug].astro b/packages/astro/test/fixtures/routing-priority/src/pages/[slug].astro
new file mode 100644
index 000000000..409942844
--- /dev/null
+++ b/packages/astro/test/fixtures/routing-priority/src/pages/[slug].astro
@@ -0,0 +1,27 @@
+---
+	export async function getStaticPaths() {
+		return [
+			{
+				params: { slug: "slug-1" },
+			},
+			{
+				params: { slug: "slug-2" },
+			}
+		]
+	}
+---
+
+<html lang="en">
+
+<head>
+	<meta charset="utf-8" />
+	<meta name="viewport" content="width=device-width" />
+	<title>Routing</title>
+</head>
+
+<body>
+	<h1>[slug].astro</h1>
+	<p>{Astro.params.slug}</p>
+</body>
+
+</html>
diff --git a/packages/astro/test/fixtures/routing-priority/src/to-inject.astro b/packages/astro/test/fixtures/routing-priority/src/to-inject.astro
new file mode 100644
index 000000000..4c5b6428f
--- /dev/null
+++ b/packages/astro/test/fixtures/routing-priority/src/to-inject.astro
@@ -0,0 +1,12 @@
+---
+---
+<html lang="en">
+	<head>
+		<meta charset="utf-8" />
+		<meta name="viewport" content="width=device-width" />
+		<title>Routing</title>
+	</head>
+	<body>
+		<h1>to-inject.astro</h1>
+	</body>
+</html>
diff --git a/packages/astro/test/routing-priority.test.js b/packages/astro/test/routing-priority.test.js
index ef2daf006..ca093fd5c 100644
--- a/packages/astro/test/routing-priority.test.js
+++ b/packages/astro/test/routing-priority.test.js
@@ -1,140 +1,140 @@
 import { expect } from 'chai';
 import { load as cheerioLoad } from 'cheerio';
-import path from 'path';
 import { loadFixture } from './test-utils.js';
 
-let fixture;
-
 const routes = [
 	{
+		description: 'matches / to index.astro',
 		url: '/',
 		h1: 'index.astro',
 	},
 	{
+		description: 'matches /slug-1 to [slug].astro',
+		url: '/slug-1',
+		h1: '[slug].astro',
+		p: 'slug-1',
+	},
+	{
+		description: 'matches /slug-2 to [slug].astro',
+		url: '/slug-2',
+		h1: '[slug].astro',
+		p: 'slug-2',
+	},
+	{
+		description: 'matches /page-1 to [page].astro',
+		url: '/page-1',
+		h1: '[page].astro',
+		p: 'page-1',
+	},
+	{
+		description: 'matches /page-2 to [page].astro',
+		url: '/page-2',
+		h1: '[page].astro',
+		p: 'page-2',
+	},
+	{
+		description: 'matches /posts/post-1 to posts/[pid].astro',
 		url: '/posts/post-1',
 		h1: 'posts/[pid].astro',
 		p: 'post-1',
 	},
 	{
+		description: 'matches /posts/post-2 to posts/[pid].astro',
 		url: '/posts/post-2',
 		h1: 'posts/[pid].astro',
 		p: 'post-2',
 	},
 	{
+		description: 'matches /posts/1/2 to posts/[...slug].astro',
 		url: '/posts/1/2',
 		h1: 'posts/[...slug].astro',
 		p: '1/2',
 	},
 	{
+		description: 'matches /de to de/index.astro',
 		url: '/de',
-		h1: 'de/index.astro',
-	},
-	{
-		url: '/de/',
-		h1: 'de/index.astro',
-	},
-	{
-		url: '/de/index.html',
-		h1: 'de/index.astro',
+		h1: 'de/index.astro (priority)',
 	},
 	{
+		description: 'matches /en to [lang]/index.astro',
 		url: '/en',
 		h1: '[lang]/index.astro',
 		p: 'en',
 	},
 	{
-		url: '/en/',
-		h1: '[lang]/index.astro',
-		p: 'en',
-	},
-	{
-		url: '/en/index.html',
-		h1: '[lang]/index.astro',
-		p: 'en',
-	},
-	{
+		description: 'matches /de/1/2 to [lang]/[...catchall].astro',
 		url: '/de/1/2',
 		h1: '[lang]/[...catchall].astro',
 		p: 'de | 1/2',
 	},
 	{
+		description: 'matches /en/1/2 to [lang]/[...catchall].astro',
 		url: '/en/1/2',
 		h1: '[lang]/[...catchall].astro',
 		p: 'en | 1/2',
 	},
+	{
+		description: 'matches /injected to to-inject.astro',
+		url: '/injected',
+		h1: 'to-inject.astro'
+	},
+	{
+		description: 'matches /_injected to to-inject.astro',
+		url: '/_injected',
+		h1: 'to-inject.astro'
+	},
+	{
+		description: 'matches /injected-1 to [id].astro',
+		url: '/injected-1',
+		h1: '[id].astro',
+		p: 'injected-1'
+	},
+	{
+		description: 'matches /injected-2 to [id].astro',
+		url: '/injected-2',
+		h1: '[id].astro',
+		p: 'injected-2'
+	}
 ];
 
-describe('Routing priority', () => {
-	before(async () => {
-		fixture = await loadFixture({
-			root: './fixtures/routing-priority/',
-		});
-	});
+function appendForwardSlash(path) {
+	return path.endsWith('/') ? path : path + '/';
+}
 
+describe('Routing priority', () => {
 	describe('build', () => {
+		let fixture;
+
 		before(async () => {
+			fixture = await loadFixture({
+				root: './fixtures/routing-priority/',
+			});
 			await fixture.build();
 		});
 
-		it('matches / to index.astro', async () => {
-			const html = await fixture.readFile('/index.html');
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('index.astro');
-		});
-
-		it('matches /posts/post-1 to posts/[pid].astro', async () => {
-			const html = await fixture.readFile('/posts/post-1/index.html');
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('posts/[pid].astro');
-			expect($('p').text()).to.equal('post-1');
-		});
-
-		it('matches /posts/1/2 to posts/[...slug].astro', async () => {
-			const html = await fixture.readFile('/posts/1/2/index.html');
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('posts/[...slug].astro');
-			expect($('p').text()).to.equal('1/2');
-		});
-
-		it('matches /de to de/index.astro', async () => {
-			const html = await fixture.readFile('/de/index.html');
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('de/index.astro (priority)');
-		});
-
-		it('matches /en to [lang]/index.astro', async () => {
-			const html = await fixture.readFile('/en/index.html');
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('[lang]/index.astro');
-			expect($('p').text()).to.equal('en');
-		});
+		routes.forEach(({ description, url, h1, p }) => {
+			it(description, async () => {
+				const html = await fixture.readFile(`${appendForwardSlash(url)}index.html`);
+				const $ = cheerioLoad(html);
 
-		it('matches /de/1/2 to [lang]/[...catchall].astro', async () => {
-			const html = await fixture.readFile('/de/1/2/index.html');
-			const $ = cheerioLoad(html);
+				expect($('h1').text()).to.equal(h1);
 
-			expect($('h1').text()).to.equal('[lang]/[...catchall].astro');
-			expect($('p').text()).to.equal('de | 1/2');
-		});
-
-		it('matches /en/1/2 to [lang]/[...catchall].astro', async () => {
-			const html = await fixture.readFile('/en/1/2/index.html');
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('[lang]/[...catchall].astro');
-			expect($('p').text()).to.equal('en | 1/2');
+				if (p) {
+					expect($('p').text()).to.equal(p);
+				}
+			});
 		});
 	});
 
 	describe('dev', () => {
+		let fixture;
 		let devServer;
 
 		before(async () => {
+			fixture = await loadFixture({
+				root: './fixtures/routing-priority/',
+			});
+
 			devServer = await fixture.startDevServer();
 		});
 
@@ -142,91 +142,42 @@ describe('Routing priority', () => {
 			await devServer.stop();
 		});
 
-		it('matches / to index.astro', async () => {
-			const html = await fixture.fetch('/').then((res) => res.text());
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('index.astro');
-		});
-
-		it('matches /posts/post-1 to /posts/[pid].astro', async () => {
-			const html = await fixture.fetch('/posts/post-1').then((res) => res.text());
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('posts/[pid].astro');
-			expect($('p').text()).to.equal('post-1');
-		});
-
-		it('matches /posts/1/2 to /posts/[...slug].astro', async () => {
-			const html = await fixture.fetch('/posts/1/2').then((res) => res.text());
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('posts/[...slug].astro');
-			expect($('p').text()).to.equal('1/2');
-		});
-
-		it('matches /de to de/index.astro', async () => {
-			const html = await fixture.fetch('/de').then((res) => res.text());
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('de/index.astro (priority)');
-			expect($('p').text()).to.equal('de');
-		});
-
-		it('matches /de/ to de/index.astro', async () => {
-			const html = await fixture.fetch('/de/').then((res) => res.text());
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('de/index.astro (priority)');
-			expect($('p').text()).to.equal('de');
-		});
-
-		it('matches /de/index.html to de/index.astro', async () => {
-			const html = await fixture.fetch('/de/index.html').then((res) => res.text());
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('de/index.astro (priority)');
-			expect($('p').text()).to.equal('de');
-		});
-
-		it('matches /en to [lang]/index.astro', async () => {
-			const html = await fixture.fetch('/en').then((res) => res.text());
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('[lang]/index.astro');
-			expect($('p').text()).to.equal('en');
-		});
-
-		it('matches /en/ to [lang]/index.astro', async () => {
-			const html = await fixture.fetch('/en/').then((res) => res.text());
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('[lang]/index.astro');
-			expect($('p').text()).to.equal('en');
-		});
-
-		it('matches /en/index.html to de/index.astro', async () => {
-			const html = await fixture.fetch('/en/index.html').then((res) => res.text());
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('[lang]/index.astro');
-			expect($('p').text()).to.equal('en');
-		});
-
-		it('matches /de/1/2 to [lang]/[...catchall].astro', async () => {
-			const html = await fixture.fetch('/de/1/2/index.html').then((res) => res.text());
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('[lang]/[...catchall].astro');
-			expect($('p').text()).to.equal('de | 1/2');
-		});
-
-		it('matches /en/1/2 to [lang]/[...catchall].astro', async () => {
-			const html = await fixture.fetch('/en/1/2/index.html').then((res) => res.text());
-			const $ = cheerioLoad(html);
-
-			expect($('h1').text()).to.equal('[lang]/[...catchall].astro');
-			expect($('p').text()).to.equal('en | 1/2');
+		routes.forEach(({ description, url, h1, p }) => {
+			// checks URLs as written above
+			it(description, async () => {
+				const html = await fixture.fetch(url).then((res) => res.text());
+				const $ = cheerioLoad(html);
+	
+				expect($('h1').text()).to.equal(h1);
+
+				if (p) {
+					expect($('p').text()).to.equal(p);
+				}
+			});
+
+			// checks with trailing slashes, ex: '/de/' instead of '/de'
+			it(`${description} (trailing slash)`, async () => {
+				const html = await fixture.fetch(appendForwardSlash(url)).then((res) => res.text());
+				const $ = cheerioLoad(html);
+	
+				expect($('h1').text()).to.equal(h1);
+
+				if (p) {
+					expect($('p').text()).to.equal(p);
+				}
+			});
+
+			// checks with index.html, ex: '/de/index.html' instead of '/de'
+			it(`${description} (index.html)`, async () => {
+				const html = await fixture.fetch(`${appendForwardSlash(url)}index.html`).then((res) => res.text());
+				const $ = cheerioLoad(html);
+	
+				expect($('h1').text()).to.equal(h1);
+
+				if (p) {
+					expect($('p').text()).to.equal(p);
+				}
+			});
 		});
 	});
 });