redux-devtools/extension/examples/counter/test/actions/counter.spec.js

import expect from 'expect';
import { applyMiddleware } from 'redux';
import thunk from 'redux-thunk';
import * as actions from '../../actions/counter';

const middlewares = [thunk];

/*
 * Creates a mock of Redux store with middleware.
 */
function mockStore(getState, expectedActions, onLastAction) {
  if (!Array.isArray(expectedActions)) {
    throw new Error('expectedActions should be an array of expected actions.');
  }
  if (
    typeof onLastAction !== 'undefined' &&
    typeof onLastAction !== 'function'
  ) {
    throw new Error('onLastAction should either be undefined or function.');
  }

  function mockStoreWithoutMiddleware() {
    return {
      getState() {
        return typeof getState === 'function' ? getState() : getState;
      },

      dispatch(action) {
        const expectedAction = expectedActions.shift();
        expect(action).toEqual(expectedAction);
        if (onLastAction && !expectedActions.length) {
          onLastAction();
        }
        return action;
      },
    };
  }

  const mockStoreWithMiddleware = applyMiddleware(...middlewares)(
    mockStoreWithoutMiddleware
  );

  return mockStoreWithMiddleware();
}

describe('actions', () => {
  it('increment should create increment action', () => {
    expect(actions.increment()).toEqual({ type: actions.INCREMENT_COUNTER });
  });

  it('decrement should create decrement action', () => {
    expect(actions.decrement()).toEqual({ type: actions.DECREMENT_COUNTER });
  });

  it('incrementIfOdd should create increment action', (done) => {
    const expectedActions = [{ type: actions.INCREMENT_COUNTER }];
    const store = mockStore({ counter: 1 }, expectedActions, done);
    store.dispatch(actions.incrementIfOdd());
  });

  it('incrementIfOdd shouldnt create increment action if counter is even', (done) => {
    const expectedActions = [];
    const store = mockStore({ counter: 2 }, expectedActions);
    store.dispatch(actions.incrementIfOdd());
    done();
  });

  it('incrementAsync should create increment action', (done) => {
    const expectedActions = [{ type: actions.INCREMENT_COUNTER }];
    const store = mockStore({ counter: 0 }, expectedActions, done);
    store.dispatch(actions.incrementAsync(100));
  });
});