使用power-assert代替should/expect/chai

[waltcow]

在写node的单元测试的时候我们常用的断言库有

• should.js
• expect.js
• chai

user.should.have.property('name', 'test');
user.enabled.should.ok;

expect(5).to.be.a('number');
expect(res.body.data).to.be.deep.equal({});

存在的问题

• API种类繁多，需要经常翻阅文档
• 出错时反馈的信息无法准确判断引起的原因，很多时候需要配合log，或者debug的工具

Power Assert in JavaScript

Power Assert in JavaScript.

Provides descriptive assertion messages through standard assert interface.

No API is the best API.

https://github.com/power-assert-js/power-assert

和常用的断言库相比，它的优点是

• API 不需要记忆
• 错误反馈信息非常详尽

const assert = require('power-assert');

describe('test/showcase.test.js', () => {
  const arr = [ 1, 2, 3 ];

  it('power-assert', () => {
    assert(arr[1] === 10);
  });
});

// output:
4) test/showcase.test.js power-assert:

      AssertionError:   # test/showcase.test.js:6

  assert(arr[1] === 10)
         |  |   |
         |  2   false
         [1,2,3]

  [number] 10
  => 10
  [number] arr[1]
  => 2

var assert = require('assert');

describe('Array', function(){
    beforeEach(function(){
        this.ary = [1,2,3];
    });
    describe('#indexOf()', function(){
        it('should return index when the value is present', function(){
            var zero = 0, two = 2;
            assert(this.ary.indexOf(zero) === two);
        });
        it('should return -1 when the value is not present', function(){
            var minusOne = -1, two = 2;
            assert.ok(this.ary.indexOf(two) === minusOne, 'THIS IS AN ASSERTION MESSAGE');
        });
    });
});

describe('various types', function(){
    function Person(name, age) {
        this.name = name;
        this.age = age;
    }
    beforeEach(function(){
        this.types = [
            'string', 98.6, true, false, null, undefined,
            ['nested', 'array'],
            {object: true},
            NaN, Infinity,
            /^not/,
            new Person('alice', 3)
        ];
    });
    it('demo', function(){
        var index = this.types.length -1,
            bob = new Person('bob', 5);
        assert(this.types[index].name === bob.name);
    });
});

HOW TO USE

使用 babel-plugin-espower 插件

安装

npm install --save-dev babel-plugin-espower

编辑 .babelrc 文件

{
  "presets": [
    ...
  ],
  "plugins": [
    "babel-plugin-espower"
  ]
}

mocha 运行时通过 babel-register 编译文件

$(npm bin)/mocha --require babel-register test/some_test.js