jest.js

it("Menu scrolls if the hovered option is out of the viewport", () => {
  const extraOptions = [
    { label: "value D4", value: "D4" },
    { label: "value E5", value: "E5" },
    { label: "value F6", value: "F6" },
  ];
  const updatedOptions = options.concat(extraOptions);

  console.log('--- extra', updatedOptions);

  const wrapper = mount(<Menu options={updatedOptions} onChange={onChange}/>, {
    attachTo: div
  });
  const items = wrapper.find(".bg-menu__item");
  const menu = wrapper.getDOMNode();

  expect(wrapper.state().hoveredIdx).toBe(0);
  expect(items.length).toBe(6);

  items.at(4).simulate('mouseEnter');

  expect(wrapper.state().hoveredIdx).toBe(4);

  simulant.fire(menu, "keydown", { keyCode: 40 }); // Down arrow

  expect(wrapper.state().hoveredIdx).toBe(5);
  console.log('--- menu.scrollTop 2', menu.scrollTop);
});