init test and snapshot,

002_source/cms/src/__tests__/snapshot.js

@@ -0,0 +1,9 @@
+import { render } from '@testing-library/react';
+
+// CUT = Component Under Test
+import CUT from '../components/_helloworld';
+
+it('renders homepage unchanged', () => {
+  const { container } = render(<CUT />);
+  expect(container).toMatchSnapshot();
+});