chore(extension): add test (#842)

* On Linux headed mode under xvfb-run fails to properly launch the
process. It works fine without xvfb-run, we don't have environment for
that on CI, so run on macOS instead.
* Node v18.20.8 stalls on `const uuid = crypto.randomUUID();`, so use
v20 for the extension tests.

extension/tests/extension.spec.ts

@@ -0,0 +1,102 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { fileURLToPath } from 'url';
+import { chromium } from 'playwright';
+import { test as base, expect } from '../../tests/fixtures.js';
+
+import type { BrowserContext } from 'playwright';
+
+type BrowserWithExtension = {
+  userDataDir: string;
+  launch: () => Promise<BrowserContext>;
+};
+
+const test = base.extend<{ browserWithExtension: BrowserWithExtension }>({
+  browserWithExtension: async ({ mcpBrowser }, use, testInfo) => {
+    // The flags no longer work in Chrome since
+    // https://chromium.googlesource.com/chromium/src/+/290ed8046692651ce76088914750cb659b65fb17%5E%21/chrome/browser/extensions/extension_service.cc?pli=1#
+    test.skip('chromium' !== mcpBrowser, '--load-extension is not supported for official builds of Chromium');
+
+    const pathToExtension = fileURLToPath(new URL('../dist', import.meta.url));
+
+    let browserContext: BrowserContext | undefined;
+    const userDataDir = testInfo.outputPath('extension-user-data-dir');
+    await use({
+      userDataDir,
+      launch: async () => {
+        browserContext = await chromium.launchPersistentContext(userDataDir, {
+          channel: mcpBrowser,
+          // Opening the browser singleton only works in headed.
+          headless: false,
+          // Automation disables singleton browser process behavior, which is necessary for the extension.
+          ignoreDefaultArgs: ['--enable-automation'],
+          args: [
+            `--disable-extensions-except=${pathToExtension}`,
+            `--load-extension=${pathToExtension}`,
+          ],
+        });
+
+        // for manifest v3:
+        let [serviceWorker] = browserContext.serviceWorkers();
+        if (!serviceWorker)
+          serviceWorker = await browserContext.waitForEvent('serviceworker');
+
+        return browserContext;
+      }
+    });
+
+    await browserContext?.close();
+  },
+});
+
+test('navigate with extension', async ({ browserWithExtension, startClient, server }) => {
+  const browserContext = await browserWithExtension.launch();
+
+  const { client } = await startClient({
+    args: [`--connect-tool`],
+    config: {
+      browser: {
+        userDataDir: browserWithExtension.userDataDir,
+      }
+    },
+  });
+
+  expect(await client.callTool({
+    name: 'browser_connect',
+    arguments: {
+      method: 'extension'
+    }
+  })).toHaveResponse({
+    result: 'Successfully changed connection method.',
+  });
+
+  const confirmationPagePromise = browserContext.waitForEvent('page', page => {
+    return page.url().startsWith('chrome-extension://jakfalbnbhgkpmoaakfflhflbfpkailf/connect.html');
+  });
+
+  const navigateResponse = client.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.HELLO_WORLD },
+  });
+
+  const selectorPage = await confirmationPagePromise;
+  await selectorPage.getByRole('button', { name: 'Continue' }).click();
+
+  expect(await navigateResponse).toHaveResponse({
+    pageState: expect.stringContaining(`- generic [active] [ref=e1]: Hello, world!`),
+  });
+});