runSaga helper

saga.ts

import { EventEmitter } from 'events';
import { runSaga as reduxRunSaga, SagaIterator } from 'redux-saga';
import { Action } from 'typescript-fsa';

interface SagaInput {
  input?: Action<any>;
  inputs?: Array<Action<any>>;
  state?: any;
  saga: () => SagaIterator;
}

type Dispatch = (...actions: Array<Action<any>>) => void;

interface SagaOutput {
  dispatched: Array<Action<any>>;
  dispatch: Dispatch;
}

export async function runSaga(run: SagaInput): Promise<SagaOutput> {
  const { input, inputs = [], state = {}, saga } = run;
  const emitter = new EventEmitter();
  emitter.setMaxListeners(100);
  const dispatched: Array<Action<any>> = [];
  const dispatch = (...actions: Array<Action<any>>) =>
    actions.forEach(a => emitter.emit('action', a));
  const promise = reduxRunSaga(
    {
      subscribe: (callback: any) => {
        emitter.on('action', callback);
        return () => {
          emitter.removeListener('action', callback);
        };
      },
      dispatch: (action: Action<any>) => dispatched.push(action),
      getState: () => state
    },
    saga
  );
  const allInputs = input ? [input] : inputs;
  dispatch(...allInputs);
  await promise;
  return { dispatched, dispatch };
}

windowSaga.spec.ts

describe('Window manager saga', () => {
  let saga: () => SagaIterator;

  beforeEach(() => {
    saga = windowManagerSaga();
  });

  describe('on splash ready', () => {
    it('should put action to show splash', async () => {
      const { dispatched } = await runSaga({
        saga,
        input: splashActions.ready()
      });

      expect(dispatched).toContainEqual(splashActions.show());
    });
  });
});