javascript - Mocha 全局范围界定问题

Question

我在围绕我正在使用的全局对象进行 mocha 测试时遇到了一个大问题。我能够生成以下 MRE，它不会给出完全相同的错误，但会举例说明有问题的(错误的？)行为。任何见解将不胜感激。

我在 /lib 中有以下 main.js 文件:

exports.exec = function(){
  console.log(test);
}

然后在 /test/test.js 中执行以下操作:

var should = require('should');
var main = require('../lib/main');

global.test = {something: 1};

describe('normal test', function(){
  beforeEach(function(){
    global.test = {another: 2};
  }),

  afterEach(function(){
    delete global.test;
  });

  it ('might work with global', function(){
    main.exec();
  })
});

最后，这是test/test2.js:

var should = require('should');
var main = require('../lib/main');

global.test = {third: 3};

describe('some test', function(){
  it ('messes up global', function(){
    main.exec();
  })
});

我希望第一个测试会输出 {another:2}，第二个会输出 {third: 3}。事实上，这是我独立运行每个测试时得到的行为。例如

jeff@ubuntu:~/workspace/mocha-test$ mocha test/test2.js 

  { third: 3 }
․

  1 passing (6ms)

但是，当使用 npm 包 should 和 mocha (1.16.1) 运行两个测试时，我得到以下输出:

jeff@ubuntu:~/workspace/mocha-test$ mocha

  { another: 2 }
․․

  1 passing (6ms)
  1 failing

  1) some test messes up global:
     ReferenceError: test is not defined
      at Object.exports.exec (/home/jeff/workspace/mocha-test/lib/main.js:3:15)
      at Context.<anonymous> (/home/jeff/workspace/mocha-test/test/test2.js:8:10)
      at Test.Runnable.run (/usr/lib/node_modules/mocha/lib/runnable.js:211:32)
      at Runner.runTest (/usr/lib/node_modules/mocha/lib/runner.js:355:10)
      at /usr/lib/node_modules/mocha/lib/runner.js:401:12
      at next (/usr/lib/node_modules/mocha/lib/runner.js:281:14)
      at /usr/lib/node_modules/mocha/lib/runner.js:290:7
      at next (/usr/lib/node_modules/mocha/lib/runner.js:234:23)
      at Object._onImmediate (/usr/lib/node_modules/mocha/lib/runner.js:258:5)
      at processImmediate [as _immediateCallback] (timers.js:330:15)

Answer 1

test2.js 的结构应该是这样的:

describe('some test', function(){
  before(function (){
    global.test = {third: 3};
  });

  it ('messes up global', function(){
    main.exec();
  })
});

travisjeffery对评论中提到的GitHub问题解释道:

mocha loads the files and then runs the suites, to reliably setup your tests the setup should be within the suite.

正如@SB 指出的那样，这可能不适用于跨测试共享诸如全局变量之类的东西。