testrenderer_create.tsx

import * as TestRenderer from 'react-test-renderer';

let renderer: TestRenderer.ReactTestRenderer;
let instance: TestRenderer.ReactTestInstance;

beforeAll(() => {
  renderer = TestRenderer.create(
      <div>
        <h2>My Super-sweet Component</h2>
        <SomeComponent />
      </div>
  );
  instance = renderer.root;
});

...