test(cli): add integration test for node deprecation warnings (#20215)

Co-authored-by: Tommaso Sciortino <sciortino@gmail.com>

integration-tests/deprecation-warnings.test.ts

@@ -0,0 +1,64 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, beforeEach, afterEach } from 'vitest';
+import { TestRig } from './test-helper.js';
+
+/**
+ * integration test to ensure no node.js deprecation warnings are emitted.
+ * must run for all supported node versions as warnings may vary by version.
+ */
+describe('deprecation-warnings', () => {
+  let rig: TestRig;
+
+  beforeEach(() => {
+    rig = new TestRig();
+  });
+
+  afterEach(async () => await rig.cleanup());
+
+  it.each([
+    { command: '--version', description: 'running --version' },
+    { command: '--help', description: 'running with --help' },
+  ])(
+    'should not emit any deprecation warnings when $description',
+    async ({ command, description }) => {
+      await rig.setup(
+        `should not emit any deprecation warnings when ${description}`,
+      );
+
+      const { stderr, exitCode } = await rig.runWithStreams([command]);
+
+      // node.js deprecation warnings: (node:12345) [DEP0040] DeprecationWarning: ...
+      const deprecationWarningPattern = /\[DEP\d+\].*DeprecationWarning/i;
+      const hasDeprecationWarning = deprecationWarningPattern.test(stderr);
+
+      if (hasDeprecationWarning) {
+        const deprecationMatches = stderr.match(
+          /\[DEP\d+\].*DeprecationWarning:.*/gi,
+        );
+        const warnings = deprecationMatches
+          ? deprecationMatches.map((m) => m.trim()).join('\n')
+          : 'Unknown deprecation warning format';
+
+        throw new Error(
+          `Deprecation warnings detected in CLI output:\n${warnings}\n\n` +
+            `Full stderr:\n${stderr}\n\n` +
+            `This test ensures no deprecated Node.js modules are used. ` +
+            `Please update dependencies to use non-deprecated alternatives.`,
+        );
+      }
+
+      // only check exit code if no deprecation warnings found
+      if (exitCode !== 0) {
+        throw new Error(
+          `CLI exited with code ${exitCode} (expected 0). This may indicate a setup issue.\n` +
+            `Stderr: ${stderr}`,
+        );
+      }
+    },
+  );
+});