diff --git a/.eslintrc b/.eslintrc
index 6a304a0..54d6c4f 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -51,6 +51,7 @@
     "no-script-url": 2,
     "no-sequences": 2,
     "no-undef": 2,
+    "no-underscore-dangle": 0,
     "no-unused-vars": 2,
     "no-with": 2,
     "quotes": [2, "single"],
diff --git a/karma.conf.js b/karma.conf.js
index 28f7182..045db95 100644
--- a/karma.conf.js
+++ b/karma.conf.js
@@ -1,5 +1,6 @@
 'use strict';
 
+var RewirePlugin = require('rewire-webpack');
 var webpackConfig = require('./webpack.config.js');
 
 // Remove the bits from the shared config
@@ -7,6 +8,11 @@ var webpackConfig = require('./webpack.config.js');
 delete webpackConfig.output;
 delete webpackConfig.entry;
 
+// Add this just for testing:
+webpackConfig.plugins = [
+  new RewirePlugin(),
+];
+
 
 module.exports = function (config) {
   config.set({
diff --git a/package.json b/package.json
index 0eb55cc..07e6cc3 100644
--- a/package.json
+++ b/package.json
@@ -53,6 +53,8 @@
     "mocha": "^2.2.5",
     "node-libs-browser": "0.5.0",
     "payment-icons": "git://github.com/muffinresearch/payment-icons.git#0.0.4",
+    "rewire": "^2.1.3",
+    "rewire-webpack": "^1.0.0",
     "sinon": "1.14.1",
     "webpack": "^1.9.5",
     "webpack-dev-server": "^1.8.2"
diff --git a/public/js/user-actions.js b/public/js/user-actions.js
index 012e98b..10c97b4 100644
--- a/public/js/user-actions.js
+++ b/public/js/user-actions.js
@@ -5,26 +5,17 @@ var assign = require('object-assign');
 
 var dispatcher = require('dispatcher');
 
+//
+// A helper object to perform user-related actions.
+// Each action will dispatch messages so that stores can
+// update their state accordingly.
+//
 
-function UserActions(localDispatcher) {
-  //
-  // A helper object to perform user-related actions.
-  // Each action will dispatch messages so that stores can
-  // update their state accordingly.
-  //
-  this.dispatcher = localDispatcher;
-}
+module.exports = assign({}, {
 
+  signIn: function(accessToken) {
 
-UserActions.prototype = assign({}, {
-
-  signIn: function(accessToken, opt) {
-    opt = opt || {};
-    if (!opt.jquery) {
-      opt.jquery = $;
-    }
-
-    opt.jquery.ajax({
+    $.ajax({
       data: {
         access_token: accessToken,
       },
@@ -41,7 +32,7 @@ UserActions.prototype = assign({}, {
 
       console.log('setting CSRF token for subsequent requests:',
                   data.csrf_token);
-      opt.jquery.ajaxSetup({
+      $.ajaxSetup({
         headers: {
           'X-CSRFToken': data.csrf_token,
         },
@@ -59,14 +50,10 @@ UserActions.prototype = assign({}, {
 
   setCurrentUser: function(user) {
     console.log('UserActions: setting current user', user);
-    this.dispatcher.dispatch({
+    dispatcher.dispatch({
       actionType: 'set-user',
       user: user,
     });
   },
 
 });
-
-
-module.exports = new UserActions(dispatcher);
-module.exports.Class = UserActions;
diff --git a/public/js/user-store.js b/public/js/user-store.js
index d6d0d43..17e0c23 100644
--- a/public/js/user-store.js
+++ b/public/js/user-store.js
@@ -46,4 +46,3 @@ UserStore.prototype = assign({}, EventEmitter.prototype, {
 
 
 module.exports = new UserStore(dispatcher);
-module.exports.Class = UserStore;
diff --git a/public/jsx/views/login.jsx b/public/jsx/views/login.jsx
index f35da84..d6c8619 100644
--- a/public/jsx/views/login.jsx
+++ b/public/jsx/views/login.jsx
@@ -14,8 +14,6 @@ module.exports = React.createClass({
 
   displayName: 'LoginView',
   mixins: [Navigation],
-  UserActions: UserActions,
-  UserStore: UserStore,
 
   contextTypes: {
     router: React.PropTypes.func,
@@ -23,12 +21,12 @@ module.exports = React.createClass({
 
   componentDidMount: function() {
     var { router } = this.context;
-    this.UserStore.addSetUserListener(this.onSetUser);
-    this.UserActions.signIn(router.getCurrentQuery().access_token);
+    UserStore.addSetUserListener(this.onSetUser);
+    UserActions.signIn(router.getCurrentQuery().access_token);
   },
 
   componentWillUnmount: function() {
-    this.UserStore.removeSetUserListener(this.onSetUser);
+    UserStore.removeSetUserListener(this.onSetUser);
   },
 
   onSetUser: function() {
@@ -36,7 +34,7 @@ module.exports = React.createClass({
       console.log('ignoring events while unmounted');
       return;
     }
-    var user = this.UserStore.getCurrentUser();
+    var user = UserStore.getCurrentUser();
     if (user.is_logged_in) {
       console.log('current user is logged in; continuing to card-listing');
       this.transitionTo('card-listing');
diff --git a/tests/test.login.jsx b/tests/test.login.jsx
index 9b17c71..6dd000f 100644
--- a/tests/test.login.jsx
+++ b/tests/test.login.jsx
@@ -1,43 +1,47 @@
 'use strict';
 
-var Login = require('views/login');
+var rewire = require('rewire');
 
 var helpers = require('./helpers');
 
 describe('Login', function() {
 
   beforeEach(function() {
+    var stubs = helpers.getUserStubs();
+    this.UserActions = stubs.UserActions;
+    this.UserStore = stubs.UserStore;
+
+    var Login = rewire('views/login');
+    Login.__set__({
+      UserActions: this.UserActions,
+      UserStore: this.UserStore,
+    });
+
     var routed = helpers.getRoutedComponent(Login);
     this.Login = routed.component;
-
-    var stubs = helpers.getUserStubs();
-
-    this.Login.UserActions = stubs.UserActions;
-    this.Login.UserStore = stubs.UserStore;
   });
 
   it('should sign in on mount', function() {
     this.Login.componentDidMount();
-    assert.ok(this.Login.UserActions.signIn.called);
+    assert.ok(this.UserActions.signIn.called);
   });
 
   it('should listen to user change', function() {
     this.Login.componentDidMount();
-    var store = this.Login.UserStore;
+    var store = this.UserStore;
     assert.equal(store.addSetUserListener.firstCall.args[0],
                  this.Login.onSetUser);
   });
 
   it('should clean up user listeners', function() {
     this.Login.componentWillUnmount();
-    var store = this.Login.UserStore;
-    assert.equal(store.removeSetUserListener.firstCall.args[0],
+    assert.equal(this.UserStore.removeSetUserListener.firstCall.args[0],
                  this.Login.onSetUser);
   });
 
   it('should navigate to card-listing when user signs in', function() {
     var transition = sinon.spy(this.Login, 'transitionTo');
-    this.Login.UserStore.getCurrentUser = function() {
+    this.UserStore.getCurrentUser = function() {
       return {
         is_logged_in: true,
       };
diff --git a/tests/test.user-actions.js b/tests/test.user-actions.js
index aca0d79..498d9a4 100644
--- a/tests/test.user-actions.js
+++ b/tests/test.user-actions.js
@@ -1,6 +1,6 @@
 'use strict';
 
-var UserActions = require('user-actions');
+var rewire = require('rewire');
 
 var helpers = require('./helpers');
 
@@ -15,7 +15,14 @@ describe('UserActions', function() {
       dispatch: function() {},
     };
     sinon.spy(dispatcher, 'dispatch');
-    userActions = new UserActions.Class(dispatcher);
+
+    userActions = rewire('user-actions');
+    userActions.__set__({
+      dispatcher: dispatcher,
+      // Replace with a non-functioning stub by default until overidden.
+      '$': {},
+    });
+
   });
 
   function fakeSignInResult() {
@@ -35,11 +42,13 @@ describe('UserActions', function() {
   });
 
   it('should set user from sign-in', function() {
-    var setUser = sinon.spy(userActions, 'setCurrentUser');
     var data = fakeSignInResult();
     var jquery = helpers.fakeJquery({returnedData: data});
+    userActions.__set__('$', jquery.stub);
 
-    userActions.signIn('access-token', {jquery: jquery.stub});
+    var setUser = sinon.spy(userActions, 'setCurrentUser');
+
+    userActions.signIn('access-token');
 
     assert.deepEqual(setUser.firstCall.args[0],
                      {email: data.buyer_email, is_logged_in: true});
@@ -47,8 +56,9 @@ describe('UserActions', function() {
 
   it('should sign-in with access token', function() {
     var jquery = helpers.fakeJquery({returnedData: fakeSignInResult()});
+    userActions.__set__('$', jquery.stub);
 
-    userActions.signIn('access-token', {jquery: jquery.stub});
+    userActions.signIn('access-token');
 
     assert.equal(jquery.ajaxSpy.firstCall.args[0].data.access_token,
                  'access-token');
@@ -57,18 +67,20 @@ describe('UserActions', function() {
   it('should configure CSRF headers on sign-in', function() {
     var data = fakeSignInResult();
     var jquery = helpers.fakeJquery({returnedData: data});
+    userActions.__set__('$', jquery.stub);
 
-    userActions.signIn('access-token', {jquery: jquery.stub});
+    userActions.signIn('access-token');
 
     assert.deepEqual(jquery.ajaxSetupSpy.firstCall.args[0].headers,
                      {'X-CSRFToken': data.csrf_token});
   });
 
   it('should set signed out user on failure', function() {
-    var setUser = sinon.spy(userActions, 'setCurrentUser');
     var jquery = helpers.fakeJquery({result: 'fail'});
+    userActions.__set__('$', jquery.stub);
+    var setUser = sinon.spy(userActions, 'setCurrentUser');
 
-    userActions.signIn('access-token', {jquery: jquery.stub});
+    userActions.signIn('access-token');
 
     assert.deepEqual(setUser.firstCall.args[0],
                      {email: null, is_logged_in: false});
diff --git a/tests/test.user-store.js b/tests/test.user-store.js
index 1b39b50..96958fe 100644
--- a/tests/test.user-store.js
+++ b/tests/test.user-store.js
@@ -1,6 +1,6 @@
 'use strict';
 
-var UserStore = require('user-store');
+var rewire = require('rewire');
 
 
 describe('UserStore', function() {
@@ -18,13 +18,17 @@ describe('UserStore', function() {
   }
 
   beforeEach(function() {
+    var module = rewire('user-store');
+
     var dispatcher = {
       register: function(receiver) {
         // Reference the callback so we can dispatch messages directly.
         dispatch = receiver;
       },
     };
-    userStore = new UserStore.Class(dispatcher);
+
+    var UserStore = module.__get__('UserStore');
+    userStore = new UserStore(dispatcher);
 
     // Stub out the event emitter.
     userStore.emit = function(event) {