mock useDispatch in jest and test the params with using that dispatch action in functional component

[upd] I've changed my mind dramatically since then. Now I think mocking store(with redux-mock-store or even real store that changes its state) - and wrapping component with <Provider store={mockedStore}> - is way more reliable and convenient. Beware.

if you mock react-redux you will be able to verify arguments for useDispatch call. Also in such a case you will need to re-create useSelector's logic(that's really straightforward and actually you don't have to make mock be a hook). Also with that approach you don't need mocked store or <Provider> at all.

import { useSelector, useDispatch } from 'react-redux'; 

const mockDispatch = jest.fn();
jest.mock('react-redux', () => ({
  useSelector: jest.fn(),
  useDispatch: () => mockDispatch
}));

it('loads data on init', () => {
  const mockedDispatch = jest.fn();
  useSelector.mockImplementation((selectorFn) => selectorFn(yourMockedStoreData));
  useDispatch.mockReturnValue(mockedDispatch);
  mount(<Router><Clients history={historyMock} /></Router>);
  expect(mockDispatch).toHaveBeenCalledWith(/*arguments your expect*/);
});

import * as redux from "react-redux";
describe('dispatch mock', function(){    
    it('should mock dispatch', function(){
            //arrange
            const useDispatchSpy = jest.spyOn(redux, 'useDispatch'); 
            const mockDispatchFn = jest.fn()
            useDispatchSpy.mockReturnValue(mockDispatchFn);

            //action
            triggerYourFlow();

            //assert
            expect(mockDispatchFn).toHaveBeenCalledWith(expectedAction);

            //teardown
            useDispatchSpy.mockClear();
    })
}});

From functional component we mock dispatch like above to stop it to execute the real implementation. Hope it helps!