How to use the @stencil/core/testing.flush function in @stencil/core

it('should work a first name', async () => {
      element.first = 'Peter';
      await flush(element);
      expect(element.textContent).toEqual('Hello, my name is Peter ');
    });

it('should show the message and image', async () => {
      element.text = 'A text';
      element.image = 'http://localhost/image.jpg';

      await flush(element);

      expect(element.textContent).toEqual('A text');
      expect(element.getElementsByTagName('img')[0].attributes.getNamedItem('src').value).toEqual('http://localhost/image.jpg');
    });
  });

it('should work with both a first and a last name', async () => {
      element.first = 'Peter';
      element.last = 'Parker';
      await flush(element);
      expect(element.textContent.trim()).toEqual('Hello, World! I\'m Peter Parker');
    });
  });

it('should not render any content if there is not a match', async () => {
      await flush(element);
      expect(element.textContent).toEqual('');
    })