How can I test Thunk actions with Jest? - unit-testing

Question

I'm new to unit testing Redux-Thunk async actions using Jest.
Here is my code:
export const functionA = (a, b) => (dispatch) => {
dispatch({ type: CONSTANT_A, payload: a });
dispatch({ type: CONSTANT_B, payload: b });
}
How can I test this function using Jest?

Answer 1

You have an example in the Redux docs: http://redux.js.org/docs/recipes/WritingTests.html#async-action-creators
import configureMockStore from 'redux-mock-store'
import thunk from 'redux-thunk'
const middlewares = [thunk]
const mockStore = configureMockStore(middlewares)
describe('async actions', () => {
it('should dispatch actions of ConstantA and ConstantB', () => {
const expectedActions = [
{type: 'CONSTANT_A', payload: 'a'},
{type: 'CONSTANT_B', payload: 'b'}
]
const store = mockStore({ yourInitialState })
store.dispatch(functionA('a', 'b'))
expect(store.getActions()).toEqual(expectedActions)
})
})

Answer 2

Also, for more more convenience, you can use this module: https://www.npmjs.com/package/redux-thunk-tester
Example:
import React from 'react';
import {createStore, applyMiddleware, combineReducers} from 'redux';
import {reducer} from './example';
import ReduxThunkTester from 'redux-thunk-tester';
import thunk from 'redux-thunk';
const request = (ms) => new Promise((resolve) => {
setTimeout(() => resolve('success response'), ms);
});
const resultRequestAction = (value) => ({ type: SOME_BACKEND_REQUEST, payload: value });
const toggleLoadingAction = (value) => ({ type: TOGGLE_LOADING, payload: value });
const asyncThunkWithRequest = () => async (dispatch) => {
try {
dispatch(toggleLoadingAction(true));
const result = await request(200);
dispatch(resultRequestAction(result));
} finally {
dispatch(toggleLoadingAction(false));
}
};
const createMockStore = () => {
const reduxThunkTester = new ReduxThunkTester();
const store = createStore(
combineReducers({exampleSimple: reducer}),
applyMiddleware(
reduxThunkTester.createReduxThunkHistoryMiddleware(),
thunk
),
);
return {reduxThunkTester, store};
};
describe('Simple example.', () => {
test('Success request.', async () => {
const {store, reduxThunkTester: {getActionHistoryAsync, getActionHistoryStringifyAsync}} = createMockStore();
store.dispatch(asyncThunkWithRequest());
const actionHistory = await getActionHistoryAsync(); // need to wait async thunk (all inner dispatch)
expect(actionHistory).toEqual([
{type: 'TOGGLE_LOADING', payload: true},
{type: 'SOME_BACKEND_REQUEST', payload: 'success response'},
{type: 'TOGGLE_LOADING', payload: false},
]);
expect(store.getState().exampleSimple).toEqual({
loading: false,
result: 'success response'
});
console.log(await getActionHistoryStringifyAsync({withColor: true}));
});
});

Answer 3

I recommend you to write something like this to avoid async problems:
return store
.dispatch(actionCreators.login({}))
.then(() => expect(store.getActions()).toEqual(expectedActions));