javascript - 如何用 Jest 模拟 Axios？

Question

我在 client/index.js 中有一个函数这是使用 axios 发出请求

import axios from "axios";

const createRequest = async (url, method) => {
    const response = await axios({
        url: url,
        method: method
    });
    return response;
};

export default { createRequest };

我想用 jest 测试这个功能，所以我创建了 client/index.test.js

import { jest } from "@jest/globals";
import axios from "axios";
    
import client from "./";

jest.doMock('axios', () => jest.fn(() => Promise.resolve()));

describe("Client", () => {

    it("should call axios and return a response", async () => {
        const response = await client.createRequest('http://localhost/', 'GET');

        expect(axios).toHaveBeenCalled();
    })
})

但是当我尝试运行它时，测试失败了，我收到了这个错误

connect ECONNREFUSED 127.0.0.1:80

如果我使用 mock 而不是 doMock，那么我会收到此错误 -

ReferenceError: /Users/project/src/client/index.test.js: The module factory of `jest.mock()` is not allowed to reference any out-of-scope variables.
    Invalid variable access: jest

package.json -

{
    "name": "project",
    "version": "0.0.1",
    "main": "index.js",
    "author": "author",
    "license": "MIT",
    "private": false,
    "type": "module",
    "scripts": {
        "start": "node --experimental-json-modules --experimental-specifier-resolution=node ./src/index.js",
        "start:dev": "nodemon --experimental-json-modules --experimental-specifier-resolution=node ./src/index.js",
        "test": "node --experimental-vm-modules node_modules/.bin/jest",
        "test:dev": "node --experimental-vm-modules node_modules/.bin/jest --watch",
        "test:coverage": "node --experimental-vm-modules node_modules/.bin/jest --coverage",
        "lint": "eslint --fix .",
        "pretty": "prettier --write ."
    },
    "dependencies": {
        "axios": "^0.21.1",
        "express": "^4.17.1"
    },
    "devDependencies": {
        "babel-eslint": "^10.1.0",
        "eslint": "^7.23.0",
        "jest": "^26.6.3",
        "prettier": "^2.2.1",
        "supertest": "^6.1.3"
    },
    "jest": { "testEnvironment": "node" }
}

我在 Node 环境中运行它， Node 版本是 14.16.0 , Jest 版本是 26.6.3 .
请帮助确定这种方法有什么问题以及如何解决它。

Answer 1

jest.doMock(moduleName, factory, options)方法不会自动提升到代码块的顶部。这意味着 axios createRequest 中使用的函数功能仍将是原始功能。
您需要使用 jest.mock() .
例如。index.js :

import axios from 'axios';

const createRequest = async (url, method) => {
  const response = await axios({
    url: url,
    method: method,
  });
  return response;
};

export default { createRequest };

index.test.js :

import axios from 'axios';
import client from './';

jest.mock('axios', () => jest.fn(() => Promise.resolve('teresa teng')));

describe('Client', () => {
  it('should call axios and return a response', async () => {
    const response = await client.createRequest('http://localhost/', 'GET');
    expect(axios).toHaveBeenCalled();
    expect(response).toEqual('teresa teng');
  });
});

单元测试结果:

 PASS  examples/67101502/index.test.js (11.503 s)
  Client
    ✓ should call axios and return a response (4 ms)

----------|---------|----------|---------|---------|-------------------
File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
----------|---------|----------|---------|---------|-------------------
All files |     100 |      100 |     100 |     100 |                   
 index.js |     100 |      100 |     100 |     100 |                   
----------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        13.62 s