How do I test Redux reducers effectively?

How do I test Redux reducers effectively?

To test Redux reducers, you can use a testing library like Jest. Start by creating test cases for each action your reducer handles.

Can you show me an example of a test case for a reducer?

Sure! Here's a simple example:

import reducer from './reducer';
import { ACTION_TYPE } from './actions';

test('should handle ACTION_TYPE', () => {
  const initialState = { count: 0 };
  const action = { type: ACTION_TYPE, payload: 1 };
  const newState = reducer(initialState, action);
  expect(newState.count).toBe(1);
});

What should I do if my reducer is not returning the expected state?

If your reducer isn't returning the expected state, check the action type and payload. Ensure your switch cases are correctly set up and that you're returning a new state object.