test: component/spinner (#556)

- covers accessibility
- provides explainer for aria-busy and aria-live tags.

src/components/spinner/spinner.test.ts

@@ -0,0 +1,25 @@
+import { expect, fixture, html } from '@open-wc/testing';
+
+import '../../../dist/shoelace.js';
+import type SlSpinner from './spinner';
+
+describe('<sl-spinner>', () => {
+  let el: SlSpinner;
+
+  describe('when provided no parameters', () => {
+    before(async () => {
+      el = await fixture<SlSpinner>(html` <sl-spinner></sl-spinner> `);
+    });
+
+    it('should render a component that passes accessibility test.', async () => {
+      await expect(el).to.be.accessible();
+    });
+
+    it('should defer updates to screen reader users via aria-live="polite".', async () => {
+      // https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/ARIA_Live_Regions
+      const base = el.shadowRoot?.querySelector('[part="base"]') as SVGElement;
+      await expect(base).have.attribute('aria-busy', 'true');
+      await expect(base).have.attribute('aria-live', 'polite');
+    });
+  });
+});