@harvest-profit/redux-saga-tester

redux-saga-tester

Full redux environment testing helper for redux-saga.

redux-saga is a great library that provides an easy way to test your sagas step-by-step, but it's tightly coupled to the saga implementation. Try a non-breaking reorder of the internal yields, and the tests will fail.

This tester library provides a full redux environment to run your sagas in, taking a black-box approach to testing. You can dispatch actions, observe the state of the store at any time, retrieve a history of actions and listen for specific actions to occur.

Getting Started

Installation

$ npm install --save-dev redux-saga-tester

Basic Example

Suppose we have a saga that waits for a START action, performs some async (or sync) actions (eg. fetching data from an API), and dispatches a SUCCESS action upon completion. Here's how we would test it:

import ourSaga from './saga';

describe('ourSaga test', () => {
    let sagaTester = null;

    beforeEach(() => {
        // Init code
        sagaTester = new SagaTester({ initialState });
        sagaTester.start(ourSaga);
    });

    it('should retrieve data from the server and send a SUCCESS action', async () => {
        // Our test (Actions is our standard redux action component). Start the saga with the START action
        sagaTester.dispatch(Actions.actions.start());

        // Wait for the saga to finish (it emits the SUCCESS action when its done)
        await sagaTester.waitFor(Actions.types.SUCCESS);

        // Check that the success action is what we expect it to be
        expect(sagaTester.getLatestCalledAction()).to.deep.equal(
            Actions.actions.success({ data: expectedData })
        );
    });
});

This is of course an example of testing a saga that contains async actions. Generally when testing it is perferred to use sync mocks. In that case, there's no need to async/await.

Full example

Can be found under the examples directory.

import chaiAsPromised from 'chai-as-promised';
import { call, take, put } from 'redux-saga/effects';
import SagaTester from 'redux-saga-tester';

chai.use(chaiAsPromised);

const someValue = 'SOME_VALUE';
const someResult = 'SOME_RESULT';
const someOtherValue = 'SOME_OTHER_VALUE';
const middlewareMeta = 'MIDDLEWARE_TEST';
const fetchRequestActionType = 'FETCH_REQUEST'
const fetchSuccessActionType = 'FETCH_SUCCESS'

const initialState = { someKey : someValue };
const reducer = (state = someValue, action) =>
    action.type === fetchSuccessActionType ? someOtherValue : state;
const middleware = store => next => action => next({
    ...action,
    meta : middlewareMeta
});
// options are passed to createSagaMiddleware
const options = { onError => console.error.bind(console) }
const fetchApi = () => someResult;

const delay = (ms) => new Promise(resolve => setTimeout(resolve, ms))

function* listenAndFetch() {
    yield take(fetchRequestActionType);
    const result = yield call(fetchApi);
    yield call(delay, 500); // For async example.
    yield put({ type : fetchSuccessActionType, payload : result });
}

it('Showcases the tester API', async () => {
    // Start up the saga tester
    const sagaTester = new SagaTester({
        initialState,
        reducers : { someKey : reducer },
        middlewares : [middleware],
        options,
    });
    sagaTester.start(listenAndFetch);

    // Check that state was populated with initialState
    expect(sagaTester.getState()).to.deep.equal(initialState);

    // Dispatch the event to start the saga
    sagaTester.dispatch({type : fetchRequestActionType});

    // Hook into the success action
    await sagaTester.waitFor(fetchSuccessActionType);

    // Check that all actions have the meta property from the middleware
    sagaTester.getCalledActions().forEach(action => {
        expect(action.meta).to.equal(middlewareMeta)
    });

    // Check that the new state was affected by the reducer
    expect(sagaTester.getState()).to.deep.equal({
        someKey : someOtherValue
    });

    // Check that the saga listens only once
    sagaTester.dispatch({ type : fetchRequestActionType });
    expect(sagaTester.numCalled(fetchRequestActionType)).to.equal(2);
    expect(sagaTester.numCalled(fetchSuccessActionType)).to.equal(1);

    // Reset the state and action list, dispatch again
    // and check that it was called
    sagaTester.reset(true);
    expect(sagaTester.wasCalled(fetchRequestActionType)).to.equal(false);
    sagaTester.dispatch({ type : fetchRequestActionType });
    expect(sagaTester.wasCalled(fetchRequestActionType)).to.equal(true);
})

API

new SagaTester(options) => sagaTester

Create a new SagaTester instance.

1. options: Object
   • initialState : Object
   • reducers : Object | Function
   • middlewares : Array[Function]
   • combineReducers : Function
   • ignoreReduxActions : Boolean
   • options : Object
     • Options for createSagaMiddleware (see docs).

sagaTester.start(saga)

Starts execution of the provided saga.

sagaTester.dispatch(action)

Dispatches an action to the redux store.

sagaTester.updateState(newState)

Assigns the newState into the current state.
(Only works with the default reducer.)

sagaTester.getState() => Object

Returns the state of the redux store.

sagaTester.waitFor(actionType, futureOnly) => Promise

Returns a promise that will resolve if the specified action is dispatched to the store.

1. actionType : String
2. futureOnly : Boolean
   • Causes waitFor to only resolve if the action is called in the future.

sagaTester.wasCalled(actionType) => Boolean

Returns whether the specified was dispatched in the past.

sagaTester.numCalled(actionType) => Number

Returns the number of times an action with the given type was dispatched.

sagaTester.getLatestCalledAction() => Action

Returns the last action dispatched to the store.

sagaTester.getCalledActions() => Array[Actions]

Returns an array of all actions dispatched.

sagaTester.reset(clearActionList)

Reset the store state back to initialState.

1. clearActionList : Boolean
   • Clears the history of past actions (defaults to false).