add tests

Author: juli1

src/__tests__/App.test.tsx

@@ -0,0 +1,9 @@
+import '@testing-library/jest-dom';
+import { render } from '@testing-library/react';
+import App from '../renderer/App';
+
+describe('App', () => {
+  it('should render', () => {
+    expect(render(<App />)).toBeTruthy();
+  });
+});