Add UI test to check the retrolab settings are persisted (#281)

* Add UI test to check settings are persisted

* Add snapshots for the settings

* Update reference snapshots

* Remove networkidle wait

* Wait for menu element

* Update reference snapshots

* Go to tmpPath before taking snapshots

* More snapshots update

ui-tests/test/settings.spec.ts

@@ -0,0 +1,31 @@
+// Copyright (c) Jupyter Development Team.
+// Distributed under the terms of the Modified BSD License.
+
+import { test } from './fixtures';
+
+import { expect } from '@playwright/test';
+
+test.use({ autoGoto: false });
+
+test.describe('Settings', () => {
+  test('Should be persisted after reloading the page', async ({
+    page,
+    tmpPath
+  }) => {
+    const showHeaderPath = 'View>Show Header';
+
+    await page.goto(`tree/${tmpPath}`);
+
+    await page.menu.clickMenuItem(showHeaderPath);
+    await page.reload({ waitUntil: 'networkidle' });
+
+    await page.menu.getMenuItem(showHeaderPath);
+    expect(await page.screenshot()).toMatchSnapshot('top-hidden.png');
+
+    await page.menu.clickMenuItem(showHeaderPath);
+    await page.reload({ waitUntil: 'networkidle' });
+
+    await page.menu.getMenuItem(showHeaderPath);
+    expect(await page.screenshot()).toMatchSnapshot('top-visible.png');
+  });
+});