code: function (root, tagName) {
      return ReactTestUtils.findAllInRenderedTree(root, function (inst) {
        return ReactTestUtils.isDOMComponent(inst) && inst.tagName.toUpperCase() === tagName.toUpperCase();
      });
    }
docs: Finds all instance of components in the rendered tree that are DOM
  components with the tag name matching `tagName`.
  @return {array} an array of all the matches.