mockDOMMatrix.js

(function mockDOMMatrix() {
  class DOMMatrixMock extends DOMMatrix {
      scale = jest.fn().mockImplementation((scaleX, scaleY) => this.setScale(scaleX, scaleY));
      translate = jest.fn().mockImplementation((x, y) => this.setTranslate(x,y));

      setScale(scaleX, scaleY) {
          this.f = scaleY;
          this.e = scaleX;
          return this;
      }

      setTranslate(x,y){
          this.b = x;
          this.c = y;
          return this;
      }
  }
  
  global.DOMMatrix = DOMMatrixMock;
})();