Unit testing Stencil component

adder.spec.ts

import { TestWindow } from '@stencil/core/testing';

import { Adder } from './adder';

describe('adder', () => {
  it('should build', () => {
    expect(new Adder()).toBeTruthy();
  });

  describe('rendering', () => {
    let element: HTMLAdderElement;
    let testWindow: TestWindow;

    beforeEach(async () => {
      testWindow = new TestWindow();
      element = await testWindow.load({
        components: [Adder],
        html: '<adder></adder>'
      });
    });
  });
});