Actions must be plain objects error while testing react app - reactjs

Question

I am having problems while testing, and am not quite sure how to fix it:
Actions must be plain objects. Use custom middleware for async
actions.
13 |
14 | useEffect( () => {
> 15 | dispatch(getPostsAction())
| ^
16 | }, [])
I am using jest + enzyme, this is my test : Post.test.js
import React from 'react';
import { mount } from 'enzyme';
import Post from './Post';
import { storeFactory } from 'testUtils';
import { Provider } from 'react-redux';
jest.mock("store/actions/PostsAction")
import {getPostsAction as mockGetPostsAction} from 'store/actions/PostsAction'
const setup = (initialState = {})=>{
const store = storeFactory(initialState);
const wrapper = mount(<Provider store={store}><Post /></Provider>)
return wrapper;
}
test('getPostsAction on Post mount', ()=>{
const wrapper = setup()
expect(mockGetPostsAction).toHaveBeenCalledTimes(1)
})
This is my Post component:
import React,{useEffect} from "react"
import {useSelector, useDispatch} from 'react-redux'
import {getPostsAction} from 'store/actions/PostsAction'
function Post() {
useEffect( () => {
dispatch(getPostsAction())
}, [])
const posts= useSelector(state => state.posts.posts)
}
.....
export default Post;
This is my action: PostsAction.js
export const getPostsAction = ()=>{
return async (dispatch) =>{
try{
const {data} = await $http.get('/api/posts')
dispatch(setPosts(data.data))
}catch(e){
}
}
}
const setPosts = posts => ({
type: SET_POSTS,
payload: posts
})
EDITED:
testUtils.js
import checkPropTypes from 'check-prop-types';
import { middlewares } from 'store/store';
import { createStore, applyMiddleware } from 'redux';
import rootReducer from 'store/reducers';
.....
export const storeFactory = (initialState) => {
return createStore(rootReducer, initialState, applyMiddleware(...middlewares));
}
store/store.js
import {createStore, applyMiddleware, compose} from 'redux'
import thunk from 'redux-thunk'
import reducer from './reducers'
export const middlewares = [thunk];
const store = createStore(
reducer,
{},
applyMiddleware(...middlewares)
);
export default store
How could I fix the error? thank you.