Why is my immutable Redux store not the same in UI and test? - unit-testing

Question

I'm building up an AppHeader component that connects to a Redux store to get its props. Ideally, I'd probably do it different, but decided to use as an exercise in testing a connected component (I'm new to React).
I'm trying to test this component by using redux-mock-store, but when I get it working in tests, the UI fails. When I get it working in the UI, the tests fail.
The PROBLEM_LINE in AppHeader.component.js below, is where the symptom originates.
When set to appHeader: state.get('AppHeader'), the tests pass successfully, but the console shows:
Uncaught TypeError: state.get is not a function at
Function.mapStateToProps [as mapToProps]`
When set to appHeader: state.AppHeader, the UI correctly displays "Real App Title" inside of an but the test now throws:
TypeError: Cannot read property 'toJS' of undefined
This seems to be an issue with using Immutable.js structures. If I change both initialState variables using plain JS objects, the tests pass and the correct value is displayed. I feel like I must be using immutable incorrectly, or am not getting stores set up correctly with it.
I've read nearly all the posts returned by Google re: testing connected components/containers but most were using state.AppHeader or state.get('AppHeader') in mapStateToProps, and most except a precious few were more on how to hook up redux and react but not so much testing it.
I tried to forego using redux-mock-store, and creating my own store (i.e. a function with dispatch, subscribe, etc) but that didn't solve any problems and only created new ones. Maybe I need to reinvestigate that if that's a better way in the end.
src/index.js
import React from 'react';
import {render} from 'react-dom';
import {Provider} from 'react-redux'
import {Router, browserHistory} from 'react-router';
import {syncHistoryWithStore} from 'react-router-redux';
import configureStore from './store/configureStore';
import routes from './routes';
const store = configureStore;
const history = syncHistoryWithStore(browserHistory, store);
render(
<Provider store={store}>
<Router history={history} routes={routes} />
</Provider>,
document.getElementById('root')
);
src/store/configureStore.js
import {createStore, combineReducers} from 'redux';
import {routerReducer} from 'react-router-redux';
import * as reducers from '../ducks';
const rootReducer = combineReducers({
routing: routerReducer,
...reducers
});
export default createStore(
rootReducer
);
src/ducks/index.js
import AppHeader from './AppHeader.duck';
export {
AppHeader
};
src/ducks/AppHeader.duck.js
import {fromJS} from 'immutable';
////////////
/// Actions
const SET_APP_TITLE = 'new-react/AppHeader/SET_APP_TITLE';
////////////
/// Reducer
const initialState = fromJS({ <-- USING IMMUTABLE HERE
title: 'Real App Title'
});
export default function reducer(state = initialState, action){
switch(action.type){
case SET_APP_TITLE:
return state.set('title', action.payload.title);
default:
return state;
}
}
////////////
/// Action Creators
export function setAppTitle(title){
return {
type: SET_APP_TITLE,
payload: {title}
};
}
module.exports = reducer;
src/components/AppHeader.component.js
import React from 'react';
import {connect} from 'react-redux';
export class AppHeader extends React.PureComponent {
render() {
const appHeader = this.props.appHeader;
return (
<div className="appHeader">
<h1 className="appHeader_title">
{appHeader.title}
</h1>
</div>
);
}
}
AppHeader.propTypes = {
appHeader: React.PropTypes.object
};
const mapStateToProps = state => {
return {
appHeader: state.AppHeader.toJS() <-- PROBLEM LINE
};
}
export default connect(
mapStateToProps
)(AppHeader);
src/components/AppHeader.component.spec.js
import React from 'react';
import ReactDOM from 'react-dom';
import {mount} from 'enzyme';
import {Provider} from 'react-redux';
import configureMockStore from 'redux-mock-store'
import {fromJS} from 'immutable';
import AppHeader from './AppHeader';
let initialState = fromJS({ <-- USING IMMUTABLE AGAIN
AppHeader: {
title: 'Mock App Title'
}
});
const mockStore = configureMockStore([])(initialState);
describe('AppHeader', () => {
let component;
beforeEach(() => {
const wrapper = mount(
<Provider store={mockStore}>
<AppHeader />
</Provider>
);
component = wrapper.find('AppHeader');
});
it('renders without crashing', () => {
expect(component).toBeDefined();
});
it('shows the app title', () => {
expect(component.find('.appHeader_title').text())
.toBe('App Header Title');
});
});
All dependencies were installed in the last day or so, so are the latest version from npm install. The app itself was created with create-react-app.