尝试使用 Mocha & Sinon 存根 HTTP 调用。收到的错误：TypeError：预期会产生，但没有通过回调

Question

我一直在练习使用JSONPlaceholder、Mocha、Chai 和Sinon 进行存根以掌握这一点，稍后我将对HTTP 调用的真实实现进行单元测试。

我创建了一个function 使用Axios 来获取所有todos 并导出为像这样的存根：

const axios = require('axios');

const getAllTodos = () => {
  return axios.get('https://jsonplaceholder.typicode.com/todos').then(response => response);
};

module.exports = { getAllTodos };

然后我尝试像这样对它进行存根：

const { expect } = require('chai');
const sinon = require('sinon');
const axios = require('axios');

const { getAllTodos } = require('correct/path/to/method');

describe('Testing the todos HTTP call', () => {
  before(() => {
      sinon.stub(axios, 'get').yields(null, null, JSON.stringify([
        {
          userId: 1,
          id: 1,
          title: "delectus aut autem",
          completed: false
          },
      ]))
    });

    after(() => {
      axios.get.restore();
    });

  it('should return all todos', done => {
    getAllTodos().then(todos => {
      todos.data.forEach(todo => {
        expect(todo).to.have.property('userId');
        expect(todo).to.have.property('id');
        expect(todo).to.have.property('title');
        expect(todo).to.have.property('completed');
      });
      done();
    }).catch(done, done);
  });
});

但是，我收到以下错误：

1) Testing the todos HTTP call
       should return all todos:
     TypeError: get expected to yield, but no callback was passed. Received [https://jsonplaceholder.typicode.com/todos]

如果我对function 进行单元测试而不用存根。它就像一个魅力。这是没有被存根的单元测试：

const { expect } = require('chai');
const { getAllTodos } = require('correct/path/to/method');

describe('Testing the todos HTTP call', () => {
  it('should return all todos', done => {
    getAllTodos().then(todos => {
      todos.data.forEach(todo => {
        expect(todo).to.have.property('userId');
        expect(todo).to.have.property('id');
        expect(todo).to.have.property('title');
        expect(todo).to.have.property('completed');
      });
      done();
    }).catch(done, done);
  });
});

我得到了function 正确的断言：

Testing the todos HTTP call
    ✓ should return all todos (169ms)

我该如何解决这个问题？我做错了什么？我需要一个对初学者友好的解释来将此解决方案转化为我自己的实现。

编辑：

我一直在尝试其他方法来存根 HTTP 呼叫，它适用于互联网，但是一旦我关闭我的互联网...... stub 失败。这是我最新的代码：

describe('Testing the todos HTTP call', () => {
  let stub;

  beforeEach(() => {
    stub = sinon.stub({ getAllTodos }, 'getAllTodos');
  });

  afterEach(() => {
    stub.restore();
  });

  it('should return all todos with the right properties', () => {
    const mockedResponseObj = {
      userId: 1,
      id: 1,
      title: 'This is title',
      completed: true,
    };

    stub
      .withArgs('https://jsonplaceholder.typicode.com/todos')
      .returns(Promise.resolve(mockedResponseObj));

    const result = getAllTodos('https://jsonplaceholder.typicode.com/todos');

    expect(result.data[0]).to.have.property('userId');
    expect(result.data[0]).to.have.property('id');
    expect(result.data[0]).to.have.property('title');
    expect(result.data[0]).to.have.property('completed');
  });
});

&导出的function最新代码：

const axios = require('axios');

const getAllTodos = url => {
  return axios.get(url).then(response => response);
};

module.exports = { getAllTodos };

Answer 1

我能够通过存根 Axios 对 getALLTodos 方法进行单元测试，而它是 GET 方法，而不是像这样：

describe('Testing the todos HTTP call', () => {
  let stub;

  const mockedResponseObj = {
    userId: 1,
    id: 1,
    title: 'This is title',
    completed: true,
  };

  beforeEach(() => {
    stub = sinon.stub(axios, 'get').resolves(mockedResponseObj);
  });

  afterEach(() => {
    stub.restore();
  });

  it('should return all todos with the right properties', done => {
    getAllTodos('https://jsonplaceholder.typicode.com/todos').then(res => {
      expect(res.data[0]).to.have.keys(Object.keys(mockedResponseObj));
    });
    done();
  });
});