Add devtools test

playwright/e2e/devtools/devtools.spec.ts

@@ -0,0 +1,27 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import { test, expect } from "../../element-web-test";
+
+test.describe("Devtools", () => {
+    test.use({
+        displayName: "Alice"
+    });
+
+    test("should render the devtools", { tag: "@screenshot" }, async ({ page, homeserver, user, app }) => {
+        await app.client.createRoom({ name: "Test Room" });
+        await app.viewRoomByName("Test Room");
+
+        const composer = app.getComposer().locator("[contenteditable]");
+        await composer.fill("/devtools");
+        await composer.press("Enter");
+        const dialog = page.locator(".mx_Dialog");
+        await dialog.getByLabel("Developer mode").check();
+
+        await expect(dialog).toMatchScreenshot("devtools-dialog.png");
+    });
+});