Dispatch 在测试 Redux 动作时不是一个函数。

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英文:

Dispatch is not a function when testing a redux action

问题

我正在学习使用Jest和Enzyme为操作创建函数编写测试。这是我在React Native中使用的一个操作创建函数。

请考虑下面的代码:

import {
    FETCH_FAIL
} from './types';

export const fetchFail = (dispatch) => {
    dispatch({
        type: FETCH_FAIL,
        payload: "An error occurred. Try again later."
    });
};

我为这个操作创建函数编写了以下测试:

import configureStore from 'redux-mock-store';
import thunk from 'redux-thunk';

const middlewares = [thunk];
const mockStore = configureStore(middlewares);

test('should fail fetch', async () => {
    const payload = {
        type: FETCH_FAIL,
        payload: "An error occurred. Try again later."
    }

    const store = mockStore({ data:[], isConnected: false });
    expect(store.dispatch(actions.fetchFail())).toEqual(payload);
})

我的测试失败,出现了以下结果:

TypeError: dispatch is not a function

我做错了什么?

英文:

I'm learning to write tests for action creators with Jest and Enzyme. This is an action creator that I am using with React Native.

Please consider the code below:

import {
    FETCH_FAIL
} from './types';

export const fetchFail = (dispatch) => {
    dispatch({
        type: FETCH_FAIL,
        payload: "An error occurred. Try again later."
    });
};

I wrote the following test for this action creator:

import configureStore from 'redux-mock-store';
import thunk from 'redux-thunk';

const middlewares = [thunk];
const mockStore = configureStore(middlewares);

test('should fail fetch', async () => {
    const payload = {
        type: FETCH_FAIL,
        payload: "An error occurred. Try again later."
    }

    const store = mockStore({ data:[], isConnected: false });
    expect(store.dispatch(actions.fetchFail())).toEqual(payload);
})

My test fails with the following result:

> TypeError: dispatch is not a function

What am I doing wrong?

答案1

得分: 4

首先您需要从您的thunk返回分发的操作
```js
export const fetchFail = (dispatch) => {
    return dispatch({
        type: FETCH_FAIL,
        payload: "An error occurred. Try again later."
    });
};

然后不要调用“thunk”,而是传递引用(删除括号),因为“thunk”中间件在操作为函数时将“dispatch”作为第一个参数调用您的操作

test('should fail fetch', async () => {
    const payload = {
        type: FETCH_FAIL,
        payload: "An error occurred. Try again later."
    }

    const store = mockStore({ data:[], isConnected: false });
    // 删除fetchFail()周围的括号
    expect(store.dispatch(actions.fetchFail)).toEqual(payload);
})
英文:

First you will need to return the dispatched action from your thunk

export const fetchFail = (dispatch) => {
    return dispatch({
        type: FETCH_FAIL,
        payload: "An error occurred. Try again later."
    });
};

And then don't call the thunk but pass the reference(remove the parentheses) because the thunk middleware is calling your action passing dispatch as the first argument when the action is a function

test('should fail fetch', async () => {
    const payload = {
        type: FETCH_FAIL,
        payload: "An error occurred. Try again later."
    }

    const store = mockStore({ data:[], isConnected: false });
    // removed the parentheses around fetchFail()
    expect(store.dispatch(actions.fetchFail)).toEqual(payload);
})

huangapple
  • 本文由 发表于 2020年1月3日 23:25:47
  • 转载请务必保留本文链接:https://go.coder-hub.com/59581142.html
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