it函数接收两个参数，描述信息和包含了待测试的单元测试代码的函数：
/**
* Define a single spec. A spec should contain one or more {@link expect|expectations} that test the state of the code.
*
* A spec whose expectations all succeed will be passing and a spec with any failures will fail.
* The name `it` is a pronoun for the test target, not an abbreviation of anything. It makes the
* spec more readable by connecting the function name `it` and the argument `description` as a
* complete sentence.
* @name it
* @since 1.3.0
* @function
* @global
* @param {String} description Textual description of what this spec is checking
* @param {implementationCallback} [testFunction] Function that contains the code of your test. If not provided the test will be `pending`.
* @param {Int} [timeout={@link jasmine.DEFAULT_TIMEOUT_INTERVAL}] Custom timeout for an async spec.
* @see async
*/
it: function() {
return env.it.apply(env, arguments);
},
这里能看到其实还有第三个可选参数，timeout即超时时间。
jasmineEnv变量是个巨大的对象，包含了很多jasmine测试方法的实现：
这个it方法里，也包含了将待测试代码通过wrapTestInZone放入Zone里执行:
it函数调用SpecFactory创建一个spec实例出来，然后返回：
注意，此时只是将it函数传入的待测试代码即箭头函数，包裹成jasmine test spec，但还未真正开始执行。
箭头函数真正的执行还是在Zone里：
更多Jerry的原创文章，尽在：“汪子熙”: