对于我们.Net程序员，System.Web.Abstractions我们都非常熟悉，主要作用于Web可以实现单元测试，他是在.Net framework 3.5 sp1开始引入的,很好的解决项目表示层不好做单元测试的问题，这个库所有类都是Wrapper/Decorator模式的。今天给推荐一个IO的扩展库与System.Web.Abstractions一样的，用来支持IO实现单元测试功能。

项目简介

一个支持IO实现单元测试的扩展库，支持跨平台，与File所有API接口都一样，方便我们项目扩展、迁移。

项目结构

项目主要核心文件是IFileSystem和FileSystem。

技术架构

1、平台：基于Net4、Netstandard2.0开发

2、开发工具：Visual Studio 2017

使用方法

读取文本使用例子，使用方法与File类一样，都是使用相同API名ReadAllText，只是这个API支持可注入和可测试的。

public class MyComponent
{
readonly IFileSystem fileSystem;

// <summary>Create MyComponent with the given fileSystem implementation</summary>
public MyComponent(IFileSystem fileSystem)
    {
this.fileSystem = fileSystem;
    }
/// <summary>Create MyComponent</summary>
public MyComponent() : this( 
        fileSystem: new FileSystem() //use default implementation which calls System.IO
    )
    {
    }

public void Validate()
    {
foreach (var textFile in fileSystem.Directory.GetFiles(@"c:\", "*.txt", SearchOption.TopDirectoryOnly))
        {
var text = fileSystem.File.ReadAllText(textFile);
if (text != "Testing is awesome.")
throw new NotSupportedException("We can't go on together. It's not me, it's you.");
        }
    }
}

文件创建单元测试

        [Test]
public void Mockfile_Create_ShouldCreateNewStream()
        {
string fullPath = XFS.Path(@"c:\something\demo.txt");
var fileSystem = new MockFileSystem();
            fileSystem.AddDirectory(XFS.Path(@"c:\something"));

var sut = new MockFile(fileSystem);

            Assert.That(fileSystem.FileExists(fullPath), Is.False);

            sut.Create(fullPath).Dispose();

            Assert.That(fileSystem.FileExists(fullPath), Is.True);
        }

删除文件单元测试

        [Test]
public void MockFile_Delete_ShouldDeleteFile()
        {
var fileSystem = new MockFileSystem();
var path = XFS.Path("C:\\test");
var directory = fileSystem.Path.GetDirectoryName(path);
            fileSystem.AddFile(path, new MockFileData("Bla"));

var fileCount1 = fileSystem.Directory.GetFiles(directory, "*").Length;
            fileSystem.File.Delete(path);
var fileCount2 = fileSystem.Directory.GetFiles(directory, "*").Length;

            Assert.AreEqual(1, fileCount1, "File should have existed");
            Assert.AreEqual(0, fileCount2, "File should have been deleted");
        }

文件复制单元测试

        [Test]
public void MockFile_Copy_ShouldOverwriteFileWhenOverwriteFlagIsTrue()
        {
string sourceFileName = XFS.Path(@"c:\source\demo.txt");
var sourceContents = new MockFileData("Source content");
string destFileName = XFS.Path(@"c:\destination\demo.txt");
var fileSystem = new MockFileSystem(new Dictionary<string, MockFileData>
            {
                {sourceFileName, sourceContents},
                {destFileName, new MockFileData("Destination content")}
            });

            fileSystem.File.Copy(sourceFileName, destFileName, true);

var copyResult = fileSystem.GetFile(destFileName);
            Assert.AreEqual(copyResult.Contents, sourceContents.Contents);
        }

文件移动单元测试

 [Test]
public void MockFile_Move_ShouldMoveFileWithinMemoryFileSystem()
        {
string sourceFilePath = XFS.Path(@"c:\something\demo.txt");
string sourceFileContent = "this is some content";
var fileSystem = new MockFileSystem(new Dictionary<string, MockFileData>
            {
                {sourceFilePath, new MockFileData(sourceFileContent)},
                {XFS.Path(@"c:\somethingelse\dummy.txt"), new MockFileData(new byte[] {0})}
            });

string destFilePath = XFS.Path(@"c:\somethingelse\demo1.txt");

            fileSystem.File.Move(sourceFilePath, destFilePath);

            Assert.That(fileSystem.FileExists(destFilePath), Is.True);
            Assert.That(fileSystem.GetFile(destFilePath).TextContents, Is.EqualTo(sourceFileContent));
            Assert.That(fileSystem.FileExists(sourceFilePath), Is.False);
        }

支持 .NET Framework用法

FileInfo SomeBadApiMethodThatReturnsFileInfo(){return new FileInfo("a");}void MyFancyMethod(){var testableFileInfo = (FileInfoBase)SomeBadApiMethodThatReturnsFileInfo();    ...}

项目地址： https://github.com/Haydabase/System.IO.Abstractions

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