Need to write unit test cases for redux reducers which are using combine reducers

Question

I want to write some unit test cases which are using combnereducers() function. I have something like following.

myReducers1.js

function reducer1(state = {}, action) {
   //some logic
}

function reducer2(state = {value1: {}}, action) {
  //some logic
}

const appReducer = combineReducers({reducer1, reducer2})

export default appRecuer;

So is there any way to test the code written inside the reducer1 and reducer2? If there is then how can i reach to the reducer1 and reducer2 function which are inside myReducers1.js. I have already gone through to the Testing Redux combined reducers but this is having the different context. So please help me. Thanks in advance.

export reducer1 and reducer2 and test them indivudually (you dont need to test 'combineReducers' it is supposed to be tested by redux ;) ) — Ji aSH, Jun 05 '18 at 21:20
Are you talking about testing individual reducers? If so then just import reducer in your test file and pass mock objects to it. — Rikin, Jun 05 '18 at 21:21
All of my reducers are in a single file. And i am combining them by using combineReducers() function. — Shravan Jain, Jun 06 '18 at 10:08

score 2 · Accepted Answer · answered Jun 05 '18 at 21:24

2

using jest:

mock a prevState:

const state = {var1: value};

make sure both reducer and action are declared or imported in the test file and run your test:

test('reducer test', () => {
  expect(reducer(state, action).toBe(your result);
});

exemple:

const testAction = { type:'INCREMENT_AGE' };

const prevState = { age: 37, name: "John Doe"};

const reducer = (state, action) => (action.type === "INCREMENT_AGE" ?{...state, age: state.age + 1} : state)

test('reducer test', () => {
  expect(reducer(prevState, testAction).toEqual({name: "John Doe", age: 38});
});

answered Jun 05 '18 at 21:24

Simon Mulquin

146
6

All of my reducers are in a single file. And i am combining them by using combineReducers() function. I got the solution from your answer. Thanks for your help. – Shravan Jain Jun 06 '18 at 10:06
1

Perfect answer <3 – AmitJS94 Jun 27 '19 at 15:45

score 1 · Answer 2 · answered Jun 05 '18 at 21:28

Assuming you have exported individual reducer and action, you just call reducer with custom/desired action and pass initial state or desired state and test for changed state object.

import reducer from '../src/reducers/reducer1';
import * as actions from '../src/actions/action1';

describe('reducer1', () => {
  it('should return the initial state', () => {
    const state = reducer(undefined, {});
    expect(state.loading).toEqual(true);
  });

  it('should handle CUSTOM_ACTION', () => {
    const action = {
      type: actions.CUSTOM_ACTION
    };
    const state = reducer({}, action);

    expect(state.foo).toEqual('desired value');
  });
});

All of my reducers are in a single file. And i am combining them by using combineReducers() function. I got the solution from above answer. Thanks for your help. — Shravan Jain, Jun 06 '18 at 10:06

Need to write unit test cases for redux reducers which are using combine reducers

2 Answers2