Add 404 routing logic to Netlify redirects file (#4274)

* Add 404 routing logic to Netlify redirects file

* changeset

1 files changed, 27 insertions, 0 deletions

diff --git a/packages/integrations/netlify/test/functions/404.test.js b/packages/integrations/netlify/test/functions/404.test.js
new file mode 100644
index 000000000..1bb5d90bd
--- /dev/null
+++ b/packages/integrations/netlify/test/functions/404.test.js
@@ -0,0 +1,27 @@
+import { expect } from 'chai';
+import netlifyAdapter from '../../dist/index.js';
+import { loadFixture, testIntegration } from './test-utils.js';
+
+describe('404 page', () => {
+	/** @type {import('./test-utils').Fixture} */
+	let fixture;
+
+	before(async () => {
+		fixture = await loadFixture({
+			root: new URL('./fixtures/404/', import.meta.url).toString(),
+			output: 'server',
+			adapter: netlifyAdapter({
+				dist: new URL('./fixtures/404/dist/', import.meta.url),
+			}),
+			site: `http://example.com`,
+			integrations: [testIntegration()],
+		});
+		await fixture.build();
+	});
+
+	it('404 route is included in the redirect file', async () => {
+		const redir = await fixture.readFile('/_redirects');
+		const expr = new RegExp("/*    /.netlify/functions/entry    404");
+		expect(redir).to.match(expr);
+	});
+});