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redux-await-actions

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Waits for specific actions to be dispatched or a timeout expires.

Installation

$ npm install @moxy/redux-await-actions --save-dev

Motivation

Consider the following example:

import thunkMiddleware from 'redux-thunk';
import { createStore, applyMiddleware, compose } from 'redux';

function login(username, password) {
    return async (dispatch) => {
        dispatch({ type: 'LOGIN_START', payload: { username, password } });

        try {
            const user = await fetch('/login', {
                headers: { 'Content-Type': 'application/json' },
                method: 'POST',
                body: JSON.stringify({ username, password })
            });

            dispatch({ type: 'LOGIN_SUCCESS', payload: user });
        } catch (err) {
            dispatch({ type: 'LOGIN_FAIL', payload: err });

            throw err;
        }

        // Side-effect: fetch orders asynchronously
        // This action could be dispatched from a middleware as well instead. See below.
        dispatch(fetchOrders());
    }
}

const middlewares = [
    thunkMiddleware,
    ({ dispatch, getState }) => (next) => (action) => {
        const result = next(action);

        if (action.type === 'LOGIN_SUCCESS') {
            // Side-effect: fetch orders asynchronously
            dispatch(fetchOrders());
        }

        return result;
    }
];
const enhancer = compose(applyMiddleware(...middlewares));
const store = createStore(/* reducer */, /* initial state */, enhancer);

store.dispatch(login('username', 'password')).then(() => {
    // For the sake of this example, assume Redux provides a getActions method
    expect(store.getActions()).toContain([
        'LOGIN_START',
        'LOGIN_SUCCESS',
        'FETCH_ORDERS_SUCCESS'
    ]);
});

The assertion above will fail because FETCH_ORDERS_SUCCESS will not yet exist in the stack of actions. To solve this, one can use setTimeout explicitly in each test:

store.dispatch(login('username', 'password'));

setTimeout(() => expect(store.getActions()).toContain([
    'LOGIN_START',
    'FETCH_ORDERS_SUCCESS'
]), 50);

However, this is not pretty and is error-prone. This library makes this easier for you. It works with both redux-mock-store and real redux store. It allows you to wait out for an arbitrary number of actions dispatched asynchronously as a result a side-effect by matching the actual contents of each dispatched action with the expected contents.

Usage

In order to ensure the store passed to redux-await-actions has a consistent interface when using either store (real and mock), a store enhancer is provided as an adapter to implement getActions and clearActions for the real store. The enhancer is exported as mockStoreAdapter Check the examples below.

Example #1: action types

Supply the action types to wait for.

Real store

import awaitActions from '@moxy/redux-await-actions';
import configureStore from 'redux';
import thunkMiddleware from 'redux-thunk';

const middlewareEnhancer = compose(applyMiddleware(thunkMiddleware));
const composedEnhancers = compose(middlewareEnhancer, awaitActions.mockStoreAdapter);
const store = createStore(/* reducer */, /* initial state */, composedEnhancers);

store.dispatch(login('username', 'password'));

await waitForActions(store, ['LOGIN_START', 'FETCH_ORDERS_SUCCESS']);

Mock store

import awaitActions from '@moxy/redux-await-actions';
import configureStore from 'redux-mock-store';
import thunkMiddleware from 'redux-thunk';

const store = configureStore([thunkMiddleware])();

store.dispatch(login('username', 'password'));

await waitForActions(store, ['LOGIN_START', 'FETCH_ORDERS_SUCCESS']);

Example #2: action objects

Supply the action objects to wait for, matching a subset of the properties of the dispatched actions. It performs a deep comparison between property values of dispatched and expected actions to determine whether the expected actions are partially contained in the stack of dispatched actions.

Mock store

import awaitActions from '@moxy/redux-await-actions';
import configureStore from 'redux-mock-store';
import thunkMiddleware from 'redux-thunk';

const store = configureStore([thunkMiddleware])();

store.dispatch(login('username', 'password'));
// { type: 'LOGIN_START', payload: { username: 'username' } }
// matches
// { type: 'LOGIN_START', payload: { username: 'username', password } }
//
// { type: 'FETCH_ORDERS_SUCCESS' }
// matches
// { type: 'FETCH_ORDERS_SUCCESS', payload: orders }

await waitForActions(store, [
    {
        type: 'LOGIN_START',
        payload: { username: 'username' },
    },
    {
        type: 'FETCH_ORDERS_SUCCESS',
    },

]);

Real store

import configureStore from 'redux';
import thunkMiddleware from 'redux-thunk';

const middlewareEnhancer = compose(applyMiddleware(thunkMiddleware));
const composedEnhancers = compose(middlewareEnhancer, awaitActions.mockStoreAdapter);
const store = createStore(/* reducer */, /* initial state */, composedEnhancers);

store.dispatch(login('username', 'password'));
// { type: 'LOGIN_START', payload: { username: 'username' } }
// matches
// { type: 'LOGIN_START', payload: { username: 'username', password } }
//
// { type: 'FETCH_ORDERS_SUCCESS' }
// matches
// { type: 'FETCH_ORDERS_SUCCESS', payload: orders }

await waitForActions(store, [
    {
        type: 'LOGIN_START',
        payload: { username: 'username' },
    },
    {
        type: 'FETCH_ORDERS_SUCCESS',
    },

]);

API

awaitActions(store, actions, [options])

Returns a Promise which fulfills if all actions are dispatched before the timeout expires. The Promise has a .cancel() function which, if called, will reject the Promise.

The Promise might be rejected:

  • as a result of timeout expiration, throwing TimeoutError
  • as a result of .cancel() invocation, throwing CancelledError
  • when the action's matcher throws MismatchError

NOTE: Subsequent calls to awaitActions with the same actions should be preceded by a call to store.clearActions(), otherwise the returned Promise will resolve immediately.

store

Type: Object

The redux-mock-store or redux store enhanced with awaitActions.mockStoreAdapter.

actions

Type: Object | String | Array | Function

The actions to wait for. It can be either:

  • String: an action type string.
  • Object: an action object.
  • Array of either
    • action objects;
    • action type strings;
    • action objects mixed with action type strings.

options

timeout

Type: Number
Default: 2000

The timeout given in milliseconds.

throttleWait

Type: Number
Default: 0

Specifies the time in milliseconds that every invocation to the action's matcher take place at since the last invocation. When set to zero, throttling is disabled.

When throttling is enabled, the matcher will be called at most once per throttleWait milliseconds receiving the array of actions dispatched until that time. If the matcher does not resolve the Promise until timeout milliseconds have elapsed, the Promise is rejected throwing TimeoutError. This feature is useful when one needs to wait for several actions or a burst of actions to be dispatched, effectively skip invocations to the action's matcher until the Redux store "settles" to avoid running complex action comparison logic in the meantime and improve performance.

matcher

Type: Function
Default: awaitActions.dispatchOrderMatcher

Supplies custom behavior to specify how expected and dispatched actions should be compared. The function accepts two arguments: the array of expected actions and dispatched actions.

The matcher must either:

  • return true to indicate a match has occurred and fulfill the Promise.
  • return false to indicate a match is yet to occur and the Promise remains in pending state.
  • throw MismatchError to indicate a match will not occur anymore and reject the Promise.

Two built-in matchers are already shipped:

  • dispatchOrderMatcher performs a comparison between the specified order of expected actions against the order of arrival of dispatched actions. On the first mismatch detected, MismatchError is thrown for early rejection.
  • wasDispatchedMatcher matcher is a less strict matcher which checks whether expected actions are contained within dispatched actions.

Both matchers perform a partial deep comparison between dispatched and expected actions, as per Lodash's isMatch().

Example of a custom matcher implementation:

import awaitActions from '@moxy/redux-await-actions';
import configureStore from 'redux-mock-store';
import thunkMiddleware from 'redux-thunk';

const store = configureStore([thunkMiddleware])();
const expectedActions = [
    { type: 'LOGIN_START', payload: { username: 'username' } },
    { type: 'FETCH_ORDERS_SUCCESS' }
];

store.dispatch(login('username', 'password'));

// Throws if LOGIN_FAIL is dispatched or
// Matches when LOGIN_START and FETCH_ORDERS_SUCCESS are dispatched
awaitActions(store, expectedActions, { matcher: (expectedActions, storeActions) => {
    const hasLoginFail = storeActions.some((action) => action.type === 'LOGIN_FAIL');

    if (hasLoginFail) {
        throw new waitForActions.MismatchError();
    }

    const hasLoginStart = storeActions.some((action) => action.type === 'LOGIN_START' && action.payload.username === 'username');
    const hasFetchOrdersSuccess = storeActions.some((action) => action.type === 'FETCH_ORDERS_SUCCESS');

    return hasLoginStart && hasFetchOrdersSuccess;
}})
.then(() => {
    // Expected actions were dispatched
})
.catch((err) => {
    // MismatchError
});

Tests

$ npm test
$ npm test -- --watch during development

License

MIT License