node.js - 用 Jest 模拟继承的类

Question

我在延长 net.Socket .这样做时，我将按如下方式覆盖连接方法。

class ENIP extends Socket {
    constructor() {
        super();

        this.state = {
            session: { id: null, establishing: false, established: false },
            error: { code: null, msg: null }
        };
    }

    connect(IP_ADDR) {
        const { registerSession } = encapsulation; //returns a buffer to send

        this.state.session.establishing = true;

        return new Promise(resolve => {
            super.connect(EIP_PORT, IP_ADDR, () => { // This is what i want to mock -> super.connect
                this.state.session.establishing = false;

                this.write(registerSession());
                resolve();
            });
        });
    }
}

我要模拟底层 socket 类以便我可以模拟 super.connect .查看了 Facebook 的 docs在这件事上，我不确定如何继续为此类开发测试，因为所有方法都将扩展 super.someMethodToMock .有谁知道我应该采取的方法？如果我可以提供任何澄清细节，请告诉我。

Answer 1

您可以使用 jest.spyOn(object, methodName)在 Socket.prototype 上创建模拟方法.
例如。index.js :

import { Socket } from 'net';

const EIP_PORT = 3000;
const encapsulation = {
  registerSession() {
    return 'session';
  },
};

export class ENIP extends Socket {
  constructor() {
    super();
    this.state = {
      session: { id: null, establishing: false, established: false },
      error: { code: null, msg: null },
    };
  }

  connect(IP_ADDR) {
    const { registerSession } = encapsulation;
    this.state.session.establishing = true;

    return new Promise((resolve) => {
      super.connect(EIP_PORT, IP_ADDR, () => {
        this.state.session.establishing = false;
        this.write(registerSession());
        resolve();
      });
    });
  }
}

index.test.js :

import { ENIP } from './';
import { Socket } from 'net';

describe('ENIP', () => {
  afterAll(() => {
    jest.restoreAllMocks();
  });
  describe('#connect', () => {
    it('should pass', async () => {
      const writeSpy = jest.spyOn(Socket.prototype, 'write').mockImplementation();
      const connectSpy = jest.spyOn(Socket.prototype, 'connect').mockImplementationOnce((port, addr, callback) => {
        callback();
      });
      const enip = new ENIP();
      await enip.connect('localhost');
      expect(writeSpy).toBeCalledWith('session');
      expect(connectSpy).toBeCalledWith(3000, 'localhost', expect.any(Function));
    });
  });
});

带有覆盖率报告的单元测试结果:

 PASS  src/stackoverflow/48888509/index.test.jsx (10.43s)
  ENIP
    #connect
      ✓ should pass (7ms)

-----------|----------|----------|----------|----------|-------------------|
File       |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
-----------|----------|----------|----------|----------|-------------------|
All files  |      100 |      100 |      100 |      100 |                   |
 index.jsx |      100 |      100 |      100 |      100 |                   |
-----------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        12.357s

源代码: https://github.com/mrdulin/jest-codelab/tree/master/src/stackoverflow/48888509