如何在Jasmine测试用例中模拟offsetHeight？

Question

我正在使用Angular js 1.6并具有

功能

setHeightForTable() {
 this.$timeout(() => {
  const height = document.querySelector('#left-graph').offsetHeight;
  const newHeight = height - 78;
  angular
    .element(document.querySelector('#evalTable table-content'))
    .css('max-height', `${newHeight}px`);
});

}

我想测试一下这是我的测试用例----

describe('setHeightForTable()', () => {
    it('should set Height For Table', () => {
      document.querySelector('#left-graph').offsetHeight = 500
      $ctrl.setHeightForTable();
      timeout.flush();
    });
  });

但我收到以下错误---

See Image for reference