test: add end-to-end tests for SSR setup

This commit introduces end-to-end (e2e) tests to validate the server-side rendering (SSR) setup.

tests/legacy-cli/e2e/tests/vite/ssr-default.ts

@@ -0,0 +1,36 @@
+import assert from 'node:assert';
+import { ng } from '../../utils/process';
+import { installWorkspacePackages, uninstallPackage } from '../../utils/packages';
+import { ngServe, useSha } from '../../utils/project';
+import { getGlobalVariable } from '../../utils/env';
+
+export default async function () {
+  assert(
+    getGlobalVariable('argv')['esbuild'],
+    'This test should not be called in the Webpack suite.',
+  );
+
+  // Enable caching to test real development workflow.
+  await ng('cache', 'clean');
+  await ng('cache', 'on');
+
+  // Forcibly remove in case another test doesn't clean itself up.
+  await uninstallPackage('@angular/ssr');
+  await ng('add', '@angular/ssr', '--server-routing', '--skip-confirmation', '--skip-install');
+  await useSha();
+  await installWorkspacePackages();
+
+  const port = await ngServe();
+
+  // Verify the server is running and the API response is correct.
+  await validateResponse('/main.js', /bootstrapApplication/);
+  await validateResponse('', /Hello,/);
+  await validateResponse('/invalid', /Cannot GET \/invalid/, 404);
+
+  async function validateResponse(pathname: string, match: RegExp, status = 200): Promise<void> {
+    const response = await fetch(new URL(pathname, `http://localhost:${port}`));
+    const text = await response.text();
+    assert.match(text, match);
+    assert.equal(response.status, status);
+  }
+}