eight of the tooltip is 20px, and
        // the tooltip is centered.
        expect(contentRect.left).to.be.equal(100 + 14);
        expect(contentRect.top).to.be.equal((20 - 30)/2);

        // Also check the math, just in case.
        expect(contentRect.left).to.be.equal(divRect.width + tooltip.offset);
        expect(contentRect.top).to.be.equal((divRect.height - contentRect.height)/2);
      });

      test('tooltip is positioned correctly (left)', function() {
        var f = fixture('basic');
      