Here's how we have been pre-processing Jest tests for React.js components which require React-Router or Fluxxor.

analytics-test.js

/** @jsx React.DOM */
//tests/app/modules/analytics-test.js
jest.dontMock('../../../app/modules/Analytics.jsx');
jest.dontMock('../../TestContext');

var React = require('react/addons'),
    MyComponent = require('../../../app/modules/Analytics.jsx'),
    TestUtils = React.addons.TestUtils,
    TestContext = require('../../TestContext'),
    component = TestContext.getRouterComponent(MyComponent).component;

describe('Analytics', function() {

    it('renders the analytics module', function() {

        spyOn(component, 'addScript');
        component.addScript();
        expect(component.addScript).toHaveBeenCalled();

    });
});

Analytics.jsx

//./app/modules/Analytics.jsx

var React = require('react');
var Fluxxor = require('fluxxor');
var FluxMixin = Fluxxor.FluxMixin(React);
var paths = require('../helpers/paths');

var Analytics = React.createClass({
    displayName: 'Analytics',
    mixins: [FluxMixin],

    getStateFromFlux: function() {
        var flux = this.getFlux();
        return flux.store('AnalyticsStore').getState();
    },

    track : function() {
        this.getFlux().actions.AnalyticsActions.track(
                this.getStateFromFlux().customVars
            );
    },

    //script tags added in `render()` aren't evaluated so we need to add them to the DOM manually
    addScript : function() {
        var _gaq = _gaq || [];
        if (window !== 'undefined') {
            window._gaq = _gaq;
        }

        _gaq.push(['_setAccount', 'UA-XXXXXX-1']);

        var ga = document.createElement('script');
        ga.src = ('https:' === document.location.protocol ? 'https://ssl' :
            'http://www') + '.google-analytics.com/ga.js';
        ga.setAttribute('async', 'true');
        document.documentElement.firstChild.appendChild(ga);

    },

    componentDidMount : function() {
        this.addScript();
        this.track();
    },

    render: function() {
        return (null);
    }
});


module.exports = Analytics;

TestContext.js

// tests/TestContext.js
// used to bootstrap components that require flux and react-router
'use strict';

var Router = require('react-router'),
    Route = Router.Route,
    React = require('react/addons'),
    TestUtils = React.addons.TestUtils,
    TestLocation = require('react-router/modules/locations/TestLocation'),
    FluxxorTestUtils = require('fluxxor-test-utils'),
    FluxConstructor = require('../app/FluxConstructor.js'),
    realFlux = FluxConstructor(),
    fakeFlux = FluxxorTestUtils.fakeFlux(realFlux);

var TestContext = {
    getRouterComponent: function(targetComponent) {
        var component, mainComponent,
            div = document.createElement('div'),
            routes = [
                React.createFactory(Route)({
                    name: 'test',
                    handler: targetComponent
                })
            ];

        TestLocation.history = ['/test'];

        Router.run(routes, TestLocation, function (Handler) {
            mainComponent = React.render(React.createFactory(Handler)({flux: fakeFlux}), div);

            component = TestUtils.findRenderedComponentWithType(mainComponent,
                targetComponent);
        });

        return {
            component: component,
            mainComponent: mainComponent
        };
    }
};

module.exports = TestContext;