render() {
        const count = this.state.count;
        /**
         * What we have here, is three divs with refs (div1/2/3), but a single
         * moving cursor ref `hopRef` that "hops" around the three. We'll call the
         * `moveRef()` function several times and make sure that the hop ref
         * points to the correct divs.
         */
        return (
          <div ref={current => (this.container = current)}>
            <div
              className="first"
              ref={count % 3 === 0 ? this.hopRef : this.divOneRef}
            />
            <div
              className="second"
              ref={count % 3 === 1 ? this.hopRef : this.divTwoRef}
            />
            <div
              className="third"
              ref={count % 3 === 2 ? this.hopRef : this.divThreeRef}
            />
          </div>
        );
      }
Tests that when a ref hops around children, we can track that correctly.