如何使用jest测试reducers

Question

我有这个减速器：

import { fromJS } from 'immutable';
import { DEFAULT_ACTION, SOURCES_LOADED, SOURCES_REQUEST } from './constants';

export const initialState = fromJS({
  sources: null,
  loading: false
});

function appReducer(state = initialState, action) {
  switch (action.type) {
    case SOURCES_REQUEST:
      return state
        .set('loading', true);
    case SOURCES_LOADED:
      return state
        .set('sources', action.payload.sources)
        .set('loading', false);
    case DEFAULT_ACTION:
      return state;
    default:
      return state;
  }
}

export default appReducer;

这个测试：

import { fromJS } from 'immutable';
import reducer from '../reducer';
import * as types from '../constants';

describe('application reducers', () => {
  it('should return the initial state', () => {
    expect(reducer(undefined, {})).toEqual(fromJS(
      {
        sources: null,
        loading: false
      }
    ));
  });

  it('should handle the sources request', () => {
    expect(reducer({ loading: true }, {
      type: types.SOURCES_REQUEST
    })).toEqual(fromJS({ loading: true }));
  });
});

第二个测试失败了：

TypeError: state.set is not a function

      11 |     case SOURCES_REQUEST:
      12 |       return state
    > 13 |         .set('loading', true);
         |          ^
      14 |     case SOURCES_LOADED:
      15 |       return state
      16 |         .set('sources', action.payload.sources)

我如何才能将测试添加到这些reducers中，因为这是redux传奇，而且我正在遵循这个https://redux.js.org/recipes/writing-tests，因为它是我找到的更接近我需求的文档。

Answer 1

您的reducer期望它接收的state是一个immutable对象。

但是在您的第二个测试中，您向它传递了一个普通的javascript对象，该对象没有您试图调用的.set方法。

it('should handle the sources request', () => {
  expect(reducer(fromJS({
    loading: true
  }), {
    type: types.SOURCES_REQUEST
  })).toEqual(fromJS({
    loading: true
  }));
});

或者，在本例中，您可以向其传递undefined，而reducer将使用initialState