  var contentRect = tooltip.getBoundingClientRect();
        expect(contentRect.width).to.be.equal(70);
        expect(contentRect.height).to.be.equal(30);

        // The tooltip width is 70px, and the tooltip is 14px to the left of the target.
        // The target div height is 20, the height of the tooltip is 20px, and
        // the tooltip is centered.
        expect(contentRect.left).to.be.equal(0 - 70 - 14);
        expect(contentRect.top).to.be.equal((20 - 30)/2);

        // Also check the math, j