index.js

import { applyMiddleware } from 'redux'
import isPlainObject from 'lodash.isplainobject'

const isFunction = (arg) => typeof arg === 'function'

/**
 * @deprecated
 *
 * The Redux team does not recommend using this package for testing. Instead, check out our {@link https://redux.js.org/recipes/writing-tests testing docs} to learn more about testing Redux code.
 *
 * Testing with a mock store leads to potentially confusing behaviour, such as state not updating when actions are dispatched. Additionally, it's a lot less useful to assert on the actions dispatched rather than the observable state changes.
 *
 * You can test the entire combination of action creators, reducers, and selectors in a single test, for example:
 * ```js
 * it("should add a todo", () => {
 *   const store = makeStore(); // a user defined reusable store factory
 *
 *   store.dispatch(addTodo("Use Redux"));
 *
 *   expect(selectTodos(store.getState())).toEqual([{ text: "Use Redux", completed: false }]);
 * });
 * ```
 *
 * This avoids common pitfalls of testing each of these in isolation, such as mocked state shape becoming out of sync with the actual application.
 *
 * If you want to use `configureStore` without this visual deprecation warning, use the `legacy_configureStore` export instead.
 *
 * `import { legacy_configureStore as configureStore } from 'redux-mock-store';`
 */
export function configureStore(middlewares = []) {
  return function mockStore(getState = {}) {
    function mockStoreWithoutMiddleware() {
      let actions = []
      let listeners = []

      const self = {
        getState() {
          return isFunction(getState) ? getState(actions) : getState
        },

        getActions() {
          return actions
        },

        dispatch(action) {
          if (!isPlainObject(action)) {
            throw new Error(
              'Actions must be plain objects. ' +
                'Use custom middleware for async actions.'
            )
          }

          if (typeof action.type === 'undefined') {
            throw new Error(
              'Actions may not have an undefined "type" property. ' +
                'Have you misspelled a constant? ' +
                'Action: ' +
                JSON.stringify(action)
            )
          }

          actions.push(action)

          for (let i = 0; i < listeners.length; i++) {
            listeners[i]()
          }

          return action
        },

        clearActions() {
          actions = []
        },

        subscribe(cb) {
          if (isFunction(cb)) {
            listeners.push(cb)
          }

          return () => {
            const index = listeners.indexOf(cb)

            if (index < 0) {
              return
            }
            listeners.splice(index, 1)
          }
        },

        replaceReducer(nextReducer) {
          if (!isFunction(nextReducer)) {
            throw new Error('Expected the nextReducer to be a function.')
          }
        }
      }

      return self
    }

    const mockStoreWithMiddleware = applyMiddleware(...middlewares)(
      mockStoreWithoutMiddleware
    )

    return mockStoreWithMiddleware()
  }
}

/**
 * Create Mock Store returns a function that will create a mock store from a state
 * with the supplied set of middleware applied.
 *
 * @param middlewares The list of middleware to be applied.
 */
export const legacy_configureStore = configureStore

export default configureStore