implementing Testing a Redux Reducer that Uses Immer for State Mutation
I'm reviewing some code and I'm attempting to set up I'm currently working on a Redux reducer that uses Immer for state mutations, and I'm having trouble writing unit tests for it. My reducer looks like this: ```javascript import produce from 'immer'; const initialState = { count: 0 }; const counterReducer = (state = initialState, action) => { return produce(state, draft => { switch (action.type) { case 'INCREMENT': draft.count += 1; break; case 'DECREMENT': draft.count -= 1; break; default: break; } }); }; export default counterReducer; ``` I've attempted to test the reducer using Jest, but I'm working with an scenario where my tests don't seem to reflect the state changes as expected. Here’s a sample test case I've written: ```javascript import counterReducer from './counterReducer'; describe('counterReducer', () => { it('should increment the count', () => { const initialState = { count: 0 }; const action = { type: 'INCREMENT' }; const newState = counterReducer(initialState, action); expect(newState.count).toBe(1); }); it('should decrement the count', () => { const initialState = { count: 0 }; const action = { type: 'DECREMENT' }; const newState = counterReducer(initialState, action); expect(newState.count).toBe(-1); }); }); ``` When I run these tests, I receive the following behavior message for the decrement test: ``` Expected: -1 Received: 0 ``` After checking my code, I suspect it might be related to how Immer handles the initial state or possibly the way I am setting the `initialState` in the tests. I've also tried using different initial states, but the scenario continues. How can I accurately reflect the state changes in my tests when using Immer with Redux? Are there best practices for testing reducers that utilize Immer for state management? Is there a better approach? This is my first time working with Javascript LTS. Could someone point me to the right documentation?