mocha with redux: expected undefined to equal true - reactjs

Question

I'm trying to wrote test for my react component which using redux and react-intl:
import React from 'react';
import { expect } from 'chai';
import { shallow, mount, render } from 'enzyme';
import Navbar from 'Navbar';
import configureMockStore from 'redux-mock-store'
import thunk from 'redux-thunk'
import { Provider } from 'react-redux';
import messages from '../src/l10n/en.json'
import { IntlProvider } from 'react-intl'
const middlewares = [ thunk ]
const mockStore = configureMockStore(middlewares)
const store = mockStore({})
describe('<Navbar />', () => {
it('calls componentDidMount', () => {
const wrapper = mount(
<Provider store={store}>
<IntlProvider locale={ "en" } messages={ messages }>
<Navbar />
</IntlProvider>
</Provider>
);
expect(Navbar.prototype.componentDidMount.calledOnce).to.equal(true);
});
});
But I got this result:
<Navbar />
1) calls componentDidMount
0 passing (73ms)
1 failing
1) <Navbar /> calls componentDidMount:
AssertionError: expected undefined to equal true
Can some one give me an advise how can I fix it?

Answer 1

The error is because, componentDidMount is not spy'ed in the test. You could use sinon to do fix this issue. For instance,
import React from 'react';
import { expect } from 'chai';
import { shallow, mount, render } from 'enzyme';
import Navbar from 'Navbar';
import configureMockStore from 'redux-mock-store'
import thunk from 'redux-thunk'
import { Provider } from 'react-redux';
import messages from '../src/l10n/en.json'
import { IntlProvider } from 'react-intl'
import { spy } from 'sinon';
const middlewares = [ thunk ]
const mockStore = configureMockStore(middlewares)
const store = mockStore({})
describe('<Navbar />', () => {
it('calls componentDidMount', () => {
spy(Navbar.prototype, 'componentDidMount');
const wrapper = mount(
<Provider store={store}>
<IntlProvider locale={ "en" } messages={ messages }>
<Navbar />
</IntlProvider>
</Provider>
);
expect(Navbar.prototype.componentDidMount.calledOnce).to.equal(true);
});
});
On a side note:- If you want to use react-intl in tests, I would suggest to use helper functions as described here