Change element size using Jest

I have following code in my component

var rect = ReactDOM.findDOMNode(this).getBoundingClientRect();

I use d3js and render graph in the component. But when I run test there are any svg tags. I assume that it happens because all rect's fields equals 0.

Here is output for console.log(rect) in browser:

ClientRect {top: 89, right: 808, bottom: 689, left: 8, width: 800…}

and when I run test:

{ bottom: 0, height: 0, left: 0, right: 0, top: 0, width: 0 }

So is there a way to set size of the element?

My solution is to mock getBoundingClientRect (I'm currently using jest 16.0.1)

describe('Mock `getBoundingClientRect`', () => {
    beforeEach(() => {
        Element.prototype.getBoundingClientRect = jest.fn(() => {
            return {
                width: 120,
                height: 120,
                top: 0,
                left: 0,
                bottom: 0,
                right: 0,
            }
        });
    });
    it('should mock `getBoundingClientRect`', () => {
        const element = document.createElement('span');
        const rect = element.getBoundingClientRect();
        expect(rect.width).toEqual(120);
    });

});