redux - 开 Jest 测试: "state.get is not a function"

Question

我正在尝试使用 jest 测试计数器 reducer ，但在分派(dispatch) INCRMENT 时收到 TypeError: state.get is not a function。 这是我的代码...

// module.js
import { fromJS } from 'immutable';
...

const initialState = fromJS({
  value: 0,
});

export default function reducer(state = initialState, action) {
  switch (action.type) {
    case INCREMENT:
      return state.set('value', state.get('value') + 1);
    case DECREMENT:
      return state.set('value', state.get('value') - 1);
    case INCREMENT_IF_ODD:
      return (state % 2 !== 0) ? state.set('value', state.get('value') + 1) : state;
    default:
      return state;
  }
}

// module.test.js
import { fromJS } from 'immutable';

import reducer, { types } from './module';

const { INCREMENT, DECREMENT, INCREMENT_IF_ODD } = types;

describe('Counter reducer', () => {
  it('should return the initial state', () => {
    expect(reducer(undefined, {})).toEqual(fromJS({
      value: 0,
    }));
  });

  it(`should handle ${INCREMENT}`, () => {
    expect(reducer(0, { type: INCREMENT })).toEqual(fromJS({
      value: 1,
    }));
  });

  ...
});

我不明白我的代码有什么问题，因为它在浏览器上运行正常。

这里是错误

 FAIL  src/containers/Counter/module.test.js
  ● Counter reducer › should handle Counter/INCREMENT

    TypeError: state.get is not a function

      at reducer (src/containers/Counter/module.js:34:50)
      at Object.<anonymous> (src/containers/Counter/module.test.js:25:33)
          at new Promise (<anonymous>)
          at <anonymous>

Answer 1

错误是因为传递给reducer的store是0，所以在reducer函数内部尝试执行0.get(..)。 传递给 reducer 的第一个参数应该是初始存储:

it(`should handle ${INCREMENT}`, () => {
  const initialState = fromJS({
    value: 0,
  });

  expect(reducer(initialState, { type: INCREMENT })).toEqual(fromJS({
    value: 1,
  }));
});