用 Jest 模拟对象构造函数调用

Question

我有这样的代码，我想在更改之前进行测试，但是当控制器调用 new dao() 时我无法模拟。

//controller.js
const dao = require('./dao');

exports.callDAOProcess = () => {
  ...
  const result = new dao().getProcess();
  ...
  return result;
};

//dao.js
function dao() {
    model = require('./model');
}

dao.prototype.getProcess = function() {
    return model.getModelProcess();
}

module.exports = dao;

//model.js
exports.getModelProcess = function () {
    return 'process';
}

我可以在测试 dao.js 时模拟 getProcess，但是当我测试控制器时，我得到了真正的 getProcess 方法。我怎么能嘲笑它？ 这是我预期的测试：mock 并收到：process：

test('Testing mock::', () => {
    const dao = require('./dao');
    jest.mock('./dao', () => jest.fn());

    dao.getProcess = jest.fn(() => ('mock'));

    const result = controller.callDAOProcess();
    expect(result).toBe('mock');
});

Answer 1

jest.mock() 方法应该不在功能范围内使用。它应该在模块范围内使用。

例如

controller.js:

const dao = require('./dao');

exports.callDAOProcess = () => {
  const result = new dao().getProcess();
  return result;
};

dao.js:

function dao() {
  this.model = require('./model');
}

dao.prototype.getProcess = function () {
  return this.model.getModelProcess();
};

controller.test.js:

const dao = require('./dao');
const controller = require('./controller');

jest.mock('./dao', () => {
  const mDao = { getProcess: jest.fn() };
  return jest.fn(() => mDao);
});

describe('63144781', () => {
  test('Testing mock::', () => {
    const daoIns = new dao();
    daoIns.getProcess.mockReturnValueOnce('mock');
    const result = controller.callDAOProcess();
    expect(result).toBe('mock');
  });
});

带有覆盖率报告的单元测试结果：

 PASS  stackoverflow/63144781/controller.test.js (10.615s)
  63144781
    ✓ Testing mock:: (4ms)

---------------|---------|----------|---------|---------|-------------------
File           | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
---------------|---------|----------|---------|---------|-------------------
All files      |     100 |      100 |     100 |     100 |                   
 controller.js |     100 |      100 |     100 |     100 |                   
---------------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        11.868s