Add tests for automatic initialisation

Author: colinrotherham

packages/nhsuk.jsdom.test.mjs

@@ -0,0 +1,20 @@
+import { waitFor } from '@testing-library/dom'
+
+import { initAll } from './index.js'
+
+jest.mock('./index.js')
+
+describe('NHS.UK frontend', () => {
+  describe('Automatic initialisation', () => {
+    it('should init components on DOMContentLoaded', async () => {
+      await import('./nhsuk.js')
+
+      // Should not initialise on import
+      expect(initAll).not.toHaveBeenCalled()
+
+      // Should initialise on DOMContentLoaded
+      window.document.dispatchEvent(new Event('DOMContentLoaded'))
+      await waitFor(() => expect(initAll).toHaveBeenCalled())
+    })
+  })
+})