jest.setup.js

Object.setPrototypeOf(window, Window.prototype);

function getBorder(style) {
  const { border, borderWidth, borderTopWidth, borderLeftWidth, borderRightWidth, borderBottomWidth } = style;

  let bT = 0;
  let bR = 0;
  let bB = 0;
  let bL = 0;

  const bMatch = /(\d+)px/.exec(border || '');
  if (bMatch) {
    const w = Number(bMatch[1]);
    bT = w;
    bR = w;
    bB = w;
    bL = w;
  }

  if (borderWidth) {
    const bw = borderWidth.split(' ');
    bT = parseInt(bw[0]);
    bR = bw[1] ? parseInt(bw[1]) : bT;
    bB = bw[2] ? parseInt(bw[2]) : bT;
    bL = bw[3] ? parseInt(bw[3]) : bR;
  }

  if (borderTopWidth) { bT = parseInt(borderTopWidth); }
  if (borderLeftWidth) { bL = parseInt(borderLeftWidth); }
  if (borderRightWidth) { bR = parseInt(borderRightWidth); }
  if (borderBottomWidth) { bB = parseInt(borderBottomWidth); }

  return { bT, bR, bB, bL };
}

Object.defineProperties(window.HTMLElement.prototype, {
  // offsetLeft: {
  //   get() { return parseFloat(this.style.marginLeft) || 0; }
  // },
  // offsetTop: {
  //   get() { return parseFloat(this.style.marginTop) || 0; }
  // },
  offsetHeight: {
    get() { return parseInt(this.style.height) || 0; }
  },
  offsetWidth: {
    get() { return parseInt(this.style.width) || 0; }
  },

  clientHeight: {
    get() {
      const { bT, bB } = getBorder(this.style);
      return this.offsetHeight - bT - bB;
    }
  },
  clientWidth: {
    get() {
      const { bR, bL } = getBorder(this.style);
      return this.offsetWidth - bR - bL;
    }
  },

  scrollHeight: {
    get() {
      return this.clientHeight + 50;
    }
  },
  scrollWidth: {
    get() {
      return this.clientWidth + 50;
    }
  }
});