hello_freedom_56/test/sqrt.test.js

## 目录结构 ``` +src 源代码目录 +test 单元测试目录 +src/tostring 黑魔法之tostring ```

/**
 * Created by lenovo on 2017/6/8.
 */
var chai = require('chai');
var expect = chai.expect;
var My = require('../src/sqrt.js');

describe("sqrt", function() {

    it("4的平方根应该等于2", function() {
        expect(My.sqrt(4)).to.equal(2);
    });

    it("参数为负值时应该报错", function() {
        expect(function(){ My.sqrt(-1); }).to.throw("负值没有平方根");
    });

});