如何在自定义函数中模拟Axios

Question

问题

当axios.get()在我自己的自定义函数中时，我如何模拟它？

在这一点上我完全迷失了方向。希望有人能看到我做错了什么。

详细信息

我有下面的getString()函数，它从网站下载html，如果找到字符串，则返回值> 0，如果没有找到字符串，返回值-1。

由于getString()使用axios.get()下载html，所以我想对这个调用进行模拟。

这篇文章是我能找到的最接近我的情况的，但在他的例子中，他模拟了一个独立的axios.request()，其中我的axios.get()在我的自定义getString()中。

我的尝试是：

getString.test.js

const axios = require('axios');
const getString = require('./getString');
jest.mock('./getString', () => {
return {
baseURL: 'localhost',
get: jest.fn().mockResolvedValue({
data: 'xxx If you are the website administrator xxx'
}),
}
});

packages.json

{
"name": "jest",
"version": "1.0.0",
"description": "",
"main": "getString.js",
"scripts": {
"test": "jest"
},
"keywords": [],
"author": "",
"license": "ISC"
}

我做了npm init -y && npm install --save-dev jest，但npm run test给了我

$ npm run test
> jest@1.0.0 test /home/mje/projects/jest
> jest
sh: jest: command not found
npm ERR! code ELIFECYCLE
npm ERR! syscall spawn
npm ERR! file sh
npm ERR! errno ENOENT
npm ERR! jest@1.0.0 test: `jest`
npm ERR! spawn ENOENT
npm ERR! 
npm ERR! Failed at the jest@1.0.0 test script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm WARN Local package.json exists, but node_modules missing, did you mean to install?

简单的PoC在文档中工作。

index.js

const getString = require('./getString');
(async function(){
'use strict'
const isOk = await getString({
url:          'http://localhost',
string:       'If you are the website administrator',
timeout:      1000,
maxRedirects: 0
});
console.log(isOk);
})();

getString.js

const axios = require('axios');
const qs = require('qs');
module.exports = async (options) => {
options              = options || {};
options.url          = options.url || {};
options.string       = options.string || null;
options.timeout      = options.timeout || 1000;
options.maxRedirects = options.maxRedirects || 0;
try {
const response = await axios.get(options.url, {
timeout: options.timeout,
maxRedirects: options.maxRedirects,
validateStatus: null,
transformResponse: [function (data) {
return data.search(options.string);
}]
});
return await response.data;
} catch (error) {
return -1;
}
};

Answer 1

首先验证jest是否在您的依赖项中，如果不在，则安装

yarn add --dev jest || npm i -D jest

然后通过模拟axios而不是要测试的实现来测试您的实现。

getString的其余部分可能看起来像这个

const axios = require('axios');
const getString = require('./getString');
jest.mock('axios')
const mockResponseData = {
hello: "world"
}
describe('getString', () => {
describe('axios returning resolved promise', () => {
beforeAll(() => {
// returning transformed mock
axios.get.mockResolvedValue({
data: mockResponseData
})
})
describe('called with arguments', () => {
let result
beforeAll(() => {
result = getString({
url: 'http://localhost',
string: 'If you are the website administrator',
timeout: 1000,
maxRedirects: 0
})
})
it('should call axios.get', async () => {
await result
expect(axios.get).toHaveBeenCalledWith(
"http://localhost",
{
"maxRedirects": 0,
"timeout": 1000,
"transformResponse": [
expect.any(Function)
],
"validateStatus": null
}
)
})
it('should return the response.data', async () => {
expect(await result).toEqual(mockResponseData)
})
})
})
describe('axios returning rejected promise', () => {
beforeAll(() => {
// returning transformed mock
axios.get.mockRejectedValue({
data: mockResponseData
})
})
describe('called with arguments', () => {
let result
beforeAll(() => {
result = getString({
url: 'http://localhost',
string: 'If you are the website administrator',
timeout: 1000,
maxRedirects: 0
})
})
it('should return -1', async () => {
expect(await result).toEqual(-1)
})
})
})
})

编辑：为了实现100%的覆盖率，您还必须测试您的实现的transformResponse，为了做到这一点，您可以像这个一样模拟实现

// this is not tested
import mockResponseBody from './localMock.json';
axios.get.mockImplementation((url, { transformResponse }) =>
Promise.resolve({
data: transformResponse.reduce((acc, fn) => fn(acc), mockResponseData)
})
)

工作示例