test: add missing snapshot tests to progress-bar (#9944)

Author: web-padawan

packages/progress-bar/test/dom/__snapshots__/progress-bar.test.snap.js

@@ -0,0 +1,22 @@
+/* @web/test-runner snapshot v1 */
+export const snapshots = {};
+
+snapshots["vaadin-progress-bar host"] = 
+`<vaadin-progress-bar
+  aria-valuemax="1"
+  aria-valuemin="0"
+  role="progressbar"
+  style="--vaadin-progress-value: 0;"
+>
+</vaadin-progress-bar>
+`;
+/* end snapshot vaadin-progress-bar host */
+
+snapshots["vaadin-progress-bar shadow"] = 
+`<div part="bar">
+  <div part="value">
+  </div>
+</div>
+`;
+/* end snapshot vaadin-progress-bar shadow */
+

packages/progress-bar/test/dom/progress-bar.test.js

@@ -0,0 +1,20 @@
+import { expect } from '@vaadin/chai-plugins';
+import { fixtureSync, nextRender } from '@vaadin/testing-helpers';
+import '../../src/vaadin-progress-bar.js';
+
+describe('vaadin-progress-bar', () => {
+  let progress;
+
+  beforeEach(async () => {
+    progress = fixtureSync('<vaadin-progress-bar></vaadin-progress-bar>');
+    await nextRender();
+  });
+
+  it('host', async () => {
+    await expect(progress).dom.to.equalSnapshot();
+  });
+
+  it('shadow', async () => {
+    await expect(progress).shadowDom.to.equalSnapshot();
+  });
+});