单元测试通过但出现错误“发送后无法设置 headers”

Question

我正在为我的第一个 Express 应用程序的 API 端点编写单元测试，使用 data-structures 作为数据库的 place-holder，所有测试都通过了，但我在控制台显示“...发送后无法设置 headers”，我知道这与第三次测试中获取单个待办事项的 get 方法的参数有关，但是到现在想不出办法

import chai from 'chai';
import { app } from '../app';
import http from 'chai-http';
import db from '../db/db';

let expect = chai.expect;

chai.use(http);

describe('Test all todo endpoints at "/api/v1/todos and "/api/v1/todo/:id" with (GET, POST, GET/id, PUT)', () => {
  before(() => {});
  after(() => {});

  //GET all todos
  it('should get all todos at "/ap1/v1/todos" with GET', () => {
    return chai
      .request(app)
      .get('/api/v1/todos/')
      .then(res => {
        expect(res).to.have.status(200);
        expect(res).to.be.json;
        expect(res.body).to.be.an('object');
        expect(res.body)
          .to.have.property('success')
          .eql('true');
        expect(res.body)
          .to.have.property('message')
          .eql('todos retrieved successfully');
        expect(res.body.todos).to.be.an('array');
        expect(
          res.body.todos[Math.floor(Math.random() * res.body.todos.length)]
        ).to.have.property('id' && 'title' && 'description');
      });
  });

  //POST a todo
  it('should add a todo at "/api/v1/todos" with POST', () => {
    return chai
      .request(app)
      .post('/api/v1/todos')
      .send({ title: 'Dinner', description: 'Dinner with bae' })
      .then(res => {
        expect(res).to.have.status(201);
        expect(res).to.be.json;
        expect(res.body).to.be.an('object');
        expect(res.body)
          .to.have.property('success')
          .eql('true');
        expect(res.body)
          .to.have.property('message')
          .equal('todo added successfully');
        expect(res.body.todo).to.be.an('object');
        expect(res.body.todo)
          .to.have.property('id')
          .equal(db.length);
        expect(res.body.todo)
          .to.have.property('title')
          .equal('Dinner');
        expect(res.body.todo)
          .to.have.property('description')
          .equal('Dinner with bae');
      });
  });

//test that passes but still gives  'can't set headers after they are sent' error
  it('should get a single todo at "/api/v1/todos/:id" with GET/id', () => {
    return chai
      .request(app)
      .get('/api/v1/todos/2')
      .then(res => {
        expect(res).to.have.status(200);
        expect(res).to.be.json;
        expect(res.body).to.be.an('object');
        expect(res.body)
          .to.have.property('success')
          .eql('true');
        expect(res.body)
          .to.have.property('message')
          .equal('todo retrieved successfully');
        expect(res.body.todo).to.be.an('object');
        expect(res.body.todo)
          .to.have.property('id')
          .equal(db.length);
        expect(res.body.todo)
          .to.have.property('title')
          .equal('Dinner');
        expect(res.body.todo)
          .to.have.property('description')
          .equal('Dinner with bae');
      });
  });
});

//controllers
import db from '../db/db';

class todosController {
  getAllTodos(req, res) {
    return res.status(200).send({
      success: 'true',
      message: 'todos retrieved successfully',
      todos: db
    });
  }
  
  //controller that gets tested and gives  'can't set headers after they are sent' error
  getTodo(req, res) {
    const id = parseInt(req.params.id, 10);
    db.map(todo => {
      if (todo.id === id) {
        return res.status(200).send({
          success: 'true',
          message: 'todo retrieved successfully',
          todo
        });
      }
    });
    return res.status(400).send({
      success: 'false',
      message: 'todo does not exist'
    });
  }

  createTodo(req, res) {
    if (!req.body.title) {
      return res.status(400).send({
        success: 'false',
        message: 'title is required'
      });
    } else if (!req.body.description) {
      return res.status(400).send({
        success: 'false',
        message: 'description is required'
      });
    }

    const todo = {
      id: db.length + 1,
      title: req.body.title,
      description: req.body.description
    };

    db.push(todo);
    return res.status(201).send({
      success: 'true',
      message: 'todo added successfully',
      todo
    });
  }

  updateTodo(req, res) {
    const id = parseInt(req.params.id, 10);
    let todoFound;
    let itemIndex;
    db.map((todo, index) => {
      if (todo.id === id) {
        todoFound = todo;
        itemIndex = index;
      }
    });

    if (!todoFound) {
      return res.status(404).send({
        success: 'true',
        message: 'todo not found'
      });
    }

    if (!req.body.title) {
      return res.status(400).send({
        success: 'false',
        message: 'title is required'
      });
    } else if (!req.body.description) {
      return res.status(400).send({
        success: 'false',
        message: 'description is required'
      });
    }

    const editedTodo = {
      // @ts-ignore
      id: todoFound.id,
      // @ts-ignore
      title: req.body.title || todoFound.title,
      // @ts-ignore
      description: req.body.description || todoFound.description
    };

    db.splice(itemIndex, 1, editedTodo);

    return res.status(200).send({
      success: 'true',
      message: 'todo updated successfully',
      editedTodo
    });
  }

  deleteTodo(req, res) {
    const id = parseInt(req.params.id, 10);
    let todoFound;
    let itemIndex;
    db.map((todo, index) => {
      if (todo.id === id) {
        todoFound = todo;
        itemIndex = index;
      }
    });

    if (!todoFound) {
      return res.status(404).send({
        success: 'true',
        message: 'todo not found'
      });
    }

    db.splice(itemIndex, 1);

    return res.status(200).send({
      success: 'true',
      message: 'todo deleted successfully'
    });
  }
}

const todoController = new todosController();
export default todoController;

//routes
//import and define express framework
import express from 'express';

import todoController from '../todoControllers/todo';

//create router handler
const router = express.Router();

router.get('/api/v1/todos', todoController.getAllTodos);
router.get('/api/v1/todos/:id', todoController.getTodo); // end point that gives error
router.post('/api/v1/todos', todoController.createTodo);
router.put('/api/v1/todos/:id', todoController.updateTodo);
router.delete('/api/v1/todos/:id', todoController.deleteTodo);

export default router;

/*
Create dummy data base using data structure
*/

const todos = [
  {
    id: 1,
    title: 'lunch',
    description: 'Go for lunch by 2pm'
  }
];

//Creating module from data structure and exposing it to be used by parts of the server
export default todos;

任何有关如何修复该错误的提示都将不胜感激，console.log

Answer 1

很有可能是这个...

db.map(todo => {
  if (todo.id === id) {
    return res.status(200).send({
      success: 'true',
      message: 'todo retrieved successfully',
      todo
    });
  }

问题是您无法将响应 headers 写入已关闭的响应流。当您调用 .send 时，它会发送参数并关闭连接。但是由于此函数包含在迭代 (.map) 中，因此它会多次尝试 .send。每次 api 调用只需要调用一次发送。

Answer 2

问题可能是因为使用 map 和多个具有相同 id 的待办事项。有更好的方法使用 find.

参考：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find

const todo = db.find(todo => todo.id === id);

if (todo) {
  return res.status(200).send({
    success: 'true',
    message: 'todo retrieved successfully',
    todo
  });
}

return res.status(400).send({
  success: 'false',
  message: 'todo does not exist'
});

单元测试通过但出现错误“发送后无法设置 headers”

unit tests passes but has error 'can't set headers after they are sent'

javascript

express

mocha.js

tdd

chai