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 yield
s, 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.
$ npm install --save-dev redux-saga-tester
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.
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);
})