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:

`js
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)
const successAction = await sagaTester.waitFor(Actions.types.SUCCESS);

// Check that the success action is what we expect it to be
expect(successAction).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.

`js
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, [...args])
Starts execution of the provided saga.

1. saga : Function
* The saga generator function to start
2. [...args] : Any
Optional* Arguments to pass to the generator on start

#### 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.

The promise resolves with the matching action object.

#### 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`).