redux-saga-testing/ava/06.saga-using-selectors.test.ts

A no-brainer way of testing your Sagas

import sagaHelper from "../helper";
import { call, select, put } from "redux-saga/effects";
import avaTest, { Assertions } from "ava";

interface State {
  foo: string;
}

const loginAction = (payload: string) => ({ type: "LOGIN", payload });
const selectUsername = (state: State) => state.foo;

function* loginSaga(): any {
  const username = yield select(selectUsername);
  yield put(loginAction(username));
}

const test = sagaHelper(loginSaga(), avaTest);

test("should select the current username from the state", (result, t: Assertions) => {
  // Remember, we are not testing the selector here, just testing that the "select" function was called with a given selector function
  // The selector won't be executed (and it can't anyway, there is no state known to redux-saga on this test)
  t.deepEqual(result, select(selectUsername));
  // We return what the selector should have returned
  return "donald.drumpf";
});

test("should trigger the login action with the username we got from the state", (result, t: Assertions) => {
  t.deepEqual(result, put(loginAction("donald.drumpf")));
});

test("and then nothing", (result, t: Assertions) => {
  t.is(result, undefined);
});