刚看到这个Namespace的时候还以为是.Net Framework里自带的包，结果查了一圈无任何结果。

果断上Github，一击即中https://github.com/tathamoddie/System.IO.Abstractions


先翻译下开发者给出的简单说明，今后再慢慢使用


类似于System.Web.Abstractions的用法，System.IO也被扩展了，它能针对IO对象进行访问

Just like System.Web.Abstractions, but for System.IO. Yay for testable IO access!

只能用NuGet方式下载

NuGet only:

Install-PackageSystem.IO.Abstractions

如果有需要可以下载测试帮助包

and/or:

Install-PackageSystem.IO.Abstractions.TestingHelpers

本库最核心的2个文件是IFileSystem和FileSystem。使用IFileSystem.File.ReadAllText等方法替换掉之前的File.ReadAllText等方法。其他API也基本完全相同，除了一些我们扩展和进行测试的方法。

At the core of the library is IFileSystem and FileSystem. Instead of calling methods like File.ReadAllText directly, use IFileSystem.File.ReadAllText. We have exactly the same API, except that ours is injectable and testable.

publicclassMyComponent{readonlyIFileSystemfileSystem;//<summary>CreateMyComponentwiththegivenfileSystemimplementation</summary>publicMyComponent(IFileSystemfileSystem){this.fileSystem=fileSystem;}///<summary>CreateMyComponent</summary>publicMyComponent():this(fileSystem:newFileSystem()//usedefaultimplementationwhichcallsSystem.IO){}publicvoidValidate(){foreach(vartextFileinfileSystem.Directory.GetFiles(@"c:\","*.txt",SearchOption.TopDirectoryOnly)){vartext=fileSystem.File.ReadAllText(textFile);if(text!="Testingisawesome.")thrownewNotSupportedException("Wecan'tgoontogether.It'snotme,it'syou.");}}}

这个库中还包含了一系列测试程序，来帮助你熟悉它。虽然它不是一个成熟的文件系统，但是它一定会给你带来帮助的。

The library also ships with a series of test helpers to save you from having to mock out every call, for basic scenarios. They are not a complete copy of a real-life file system, but they'll get you most of the way there.

[Test]publicvoidMyComponent_Validate_ShouldThrowNotSupportedExceptionIfTestingIsNotAwesome(){//ArrangevarfileSystem=newMockFileSystem(newDictionary<string,MockFileData>{{@"c:\myfile.txt",newMockFileData("Testingismeh.")},{@"c:\demo\jQuery.js",newMockFileData("somejs")},{@"c:\demo\p_w_picpath.gif",newMockFileData(newbyte[]{0x12,0x34,0x56,0xd2})}});varcomponent=newMyComponent(fileSystem);try{//Actcomponent.Validate();}catch(NotSupportedExceptionex){//AssertAssert.AreEqual("Wecan'tgoontogether.It'snotme,it'syou.",ex.Message);return;}Assert.Fail("Theexpectedexceptionwasnotthrown.");}

我们甚至支持把.NET框架里不可测试的类型加入到测试程序里

We even support casting from the .NET Framework's untestable types to our testable wrappers:

FileInfoSomeBadApiMethodThatReturnsFileInfo(){returnnewFileInfo("a");}voidMyFancyMethod(){vartestableFileInfo=(FileInfoBase)SomeBadApiMethodThatReturnsFileInfo();//...}