Reducer Test sample

import configureMockStore from 'redux-mock-store';
import thunk from 'redux-thunk';
import rollDice from 'utils/rollDice';
import {
  initialState,
  monsterActions,
  monsterReducer,
  monsterAttack,
  getMonsterIsAttacking,
  getMonsterDamage,
  getMonsterDice2,
  getMonsterDice1,
  getMonsterHealth
} from './monsterSlice';
import { RootState } from 'reducers';

const mockStore = configureMockStore([thunk]);
jest.mock('utils/rollDice');

describe('Monster Slice', () => {
  describe('Reducer', () => {
    test('When initialised, return initial state', () => {
      expect(monsterReducer(undefined, {} as any)).toBe(initialState);
    });

    test('When a attack start action is fired, reset damage taken', () => {
      const nextState = monsterReducer(
        initialState,
        monsterActions.attackStart()
      );
      const rootState = { monster: nextState } as RootState;
      expect(getMonsterIsAttacking(rootState)).toEqual(true);
      expect(getMonsterDamage(rootState)).toEqual(initialState.damageTaken);
    });

    test('When a attack end action is fired, set dice values', () => {
      const nextState = monsterReducer(
        initialState,
        monsterActions.attackEnd({
          dice1Value: 3,
          dice2Value: 5
        })
      );
      const rootState = { monster: nextState } as RootState;
      expect(getMonsterIsAttacking(rootState)).toEqual(false);
      expect(getMonsterDice1(rootState)).toEqual(3);
      expect(getMonsterDice2(rootState)).toEqual(5);
    });

    test('When a take damage end action is fired, reduce health', () => {
      const nextState = monsterReducer(
        initialState,
        monsterActions.takeDamage(6)
      );
      const rootState = { monster: nextState } as RootState;
      expect(getMonsterDamage(rootState)).toEqual(6);
      expect(getMonsterHealth(rootState)).toEqual(94);
    });
  });

  describe('Thunks', () => {
    describe('monsterAttack', () => {
      test('When attacking, roll dice and return the total result', async () => {
        rollDice.mockReturnValueOnce(3).mockReturnValueOnce(5);
        const store = mockStore(initialState);
        const expectedResult = await monsterAttack(store.dispatch);
        const expectedActions = [
          monsterActions.attackStart(),
          monsterActions.attackEnd({
            dice1Value: 3,
            dice2Value: 5
          })
        ];
        expect(expectedResult).toEqual(8);
        expect(store.getActions()).toEqual(expectedActions);
      });
    });
  });
});