Rendering virtual component tree

package.json

{
  "scripts": {
    "test": "mocha test.js"
  },
  "dependencies": {
    "mocha": "^3.2.0",
    "react": "^15.4.1",
    "react-addons-test-utils": "^15.4.1",
    "react-dom": "^15.4.1",
    "react-test-renderer": "^15.4.1",
    "xpath-evaluator": "^2.0.1",
    "xpath-react": "^4.0.0"
  }
}

test.js

var React = require("react");

var ReactTestUtils = require('react-addons-test-utils');

var ReactTestRenderer = require('react-test-renderer');

var getHostComponentFromComposite = require('react-test-renderer/lib/getHostComponentFromComposite');

var Assert = require("assert");

var XPathUtils = require("xpath-react/utils");

function Foo () {
  return React.createElement(Bar);
}

function Bar () {
  return React.createElement("span", {}, "Hello world!");
}

describe("ReactTestUtils", function () {
  it("should not be able to render sub component", function () {
    var renderer = ReactTestUtils.createRenderer();

    renderer.render(React.createElement(Foo));

    var output = renderer.getRenderOutput();

    var result = XPathUtils.find(output, "count(.//span)");

    Assert.equal(result, 0);
  });
});

describe("ReactTestRenderer", function () {
  it("should be able to render sub component", function () {
    var renderer = renderer = ReactTestRenderer.create(
        React.createElement(Foo));

    var output = getHostComponentFromComposite(renderer._component)._currentElement;

    var result = XPathUtils.find(output, "count(.//span)");

    Assert.equal(result, 1);
  });
});