Difficulty Testing Asynchronous Functions in a Redux Slice with Redux Toolkit and Jest
I'm maintaining legacy code that Can someone help me understand I've spent hours debugging this and I'm trying to write unit tests for a Redux slice that uses asynchronous actions with createAsyncThunk from Redux Toolkit... I have a slice that fetches user data from an API and updates the state accordingly. Here's a simplified version of my slice: ```javascript import { createSlice, createAsyncThunk } from '@reduxjs/toolkit'; export const fetchUser = createAsyncThunk('user/fetchUser', async (userId) => { const response = await fetch(`https://api.example.com/users/${userId}`); if (!response.ok) { throw new Error('Failed to fetch'); } return response.json(); }); const userSlice = createSlice({ name: 'user', initialState: { user: null, loading: false, error: null }, reducers: {}, extraReducers: (builder) => { builder .addCase(fetchUser.pending, (state) => { state.loading = true; state.error = null; }) .addCase(fetchUser.fulfilled, (state, action) => { state.loading = false; state.user = action.payload; }) .addCase(fetchUser.rejected, (state, action) => { state.loading = false; state.error = action.error.message; }); }, }); export default userSlice.reducer; ``` I want to test the `fetchUser` thunk and ensure that the loading and error states are handled correctly. I wrote the following test: ```javascript import { configureStore } from '@reduxjs/toolkit'; import userReducer, { fetchUser } from './userSlice'; import thunk from 'redux-thunk'; import { act } from 'react-dom/test-utils'; describe('userSlice', () => { let store; beforeEach(() => { store = configureStore({ reducer: { user: userReducer }, middleware: [thunk] }); }); it('should handle fetching user data', async () => { await act(async () => { await store.dispatch(fetchUser(1)); }); const state = store.getState().user; expect(state.loading).toBe(false); expect(state.user).toBeDefined(); expect(state.error).toBeNull(); }); }); ``` However, when I run the test, I get the following error: ``` Error: Network request failed ``` It seems like Jest is trying to make an actual network request, which I want to avoid. I've tried mocking the `fetch` function using `jest.mock`, but it doesn't seem to be working properly. What is the best way to mock the asynchronous API call in this context? Any suggestions on how to structure my tests or handle mocking the fetch call properly? What's the best practice here? I've been using Javascript for about a year now. Any ideas what could be causing this? I'm on CentOS using the latest version of Javascript. What's the correct way to implement this?