Function checkDOM

specs/Modal.spec.js:201–204

(count)

    const closeTimeoutMS = 100;

    function checkDOM(count) {
      const portal = document.querySelectorAll(".ReactModalPortal");
      portal.length.should.be.eql(count);
    }

    const props = { isOpen: true, closeTimeoutMS };
    withModal(props, "hello", () => {