单元测试不可测试那些类（无抽象、静态类、静态方法）

实际上“单元测试不可测试那些类（无抽象、静态类、静态方法）”是个伪命题，因为事实是：无抽象、静态类、静态方法都是不可单元测试的。那么，如果我们要写出可测试的代码，又要用到这些静态类等，该怎么办，实际上我们需要两个步骤：

1：为它们写一个包装类，让这个包装类是抽象的（继承自接口，或者抽象类，或者方法本身是Virtual的）；

2：通知客户端程序员，使用包装类来代替原先的静态类来写业务逻辑；

实际上，微软也是这么干的，我在上一篇博文《单元测试WebForm的UI逻辑及文件上传》写到，最典型的不可测试类，那就是WebForm架构的网站中，对Response等的模拟。查看Response这个类： 

namespace System.Web
{
    public sealed class HttpResponse
    {
        ...
    }
}

很明显，如果我们在某个WebForm的后台方法中，直接使用它的话：

protected void Page_Load(object sender, EvengArgs e)
{
  this.Response.Write("test u");
}

该后台代码逻辑就无法进行单元测试了，因为类似MOQ的框架所依赖的是代码本身具有可被重写行，如果某个类本身是静态的，就无法在运行时用模拟类替换掉实际类。

所以，写一个包装类吧，我们看到微软为Response写了一个包装类，为HttpResponseWrapper：

namespace System.Web
{
    [TypeForwardedFrom("System.Web.Abstractions, Version=3.5.0.0, Culture=Neutral, PublicKeyToken=31bf3856ad364e35")]
    public class HttpResponseWrapper : HttpResponseBase
    {
        public override bool Buffer
        {
            get
            {
            }
            set
            {
            }
        }
        public override bool BufferOutput
        {
            get
            {
            }
            set
            {
            }
        }
        public override HttpCachePolicyBase Cache
        {
            get
            {
            }
        }
        public override string CacheControl
        {
            get
            {
            }
            set
            {
            }
        }
        public override string Charset
        {
            get
            {
            }
            set
            {
            }
        }
        public override CancellationToken ClientDisconnectedToken
        {
            get
            {
            }
        }
        public override Encoding ContentEncoding
        {
            get
            {
            }
            set
            {
            }
        }
        public override string ContentType
        {
            get
            {
            }
            set
            {
            }
        }
        public override HttpCookieCollection Cookies
        {
            get
            {
            }
        }
        public override int Expires
        {
            get
            {
            }
            set
            {
            }
        }
        public override DateTime ExpiresAbsolute
        {
            get
            {
            }
            set
            {
            }
        }
        public override Stream Filter
        {
            get
            {
            }
            set
            {
            }
        }
        public override NameValueCollection Headers
        {
            get
            {
            }
        }
        public override Encoding HeaderEncoding
        {
            get
            {
            }
            set
            {
            }
        }
        public override bool IsClientConnected
        {
            get
            {
            }
        }
        public override bool IsRequestBeingRedirected
        {
            get
            {
            }
        }
        public override TextWriter Output
        {
            get
            {
            }
            set
            {
            }
        }
        public override Stream OutputStream
        {
            get
            {
            }
        }
        public override string RedirectLocation
        {
            get
            {
            }
            set
            {
            }
        }
        public override string Status
        {
            get
            {
            }
            set
            {
            }
        }
        public override int StatusCode
        {
            get
            {
            }
            set
            {
            }
        }
        public override string StatusDescription
        {
            get
            {
            }
            set
            {
            }
        }
        public override int SubStatusCode
        {
            get
            {
            }
            set
            {
            }
        }
        public override bool SupportsAsyncFlush
        {
            get
            {
            }
        }
        public override bool SuppressContent
        {
            get
            {
            }
            set
            {
            }
        }
        public override bool SuppressFormsAuthenticationRedirect
        {
            get
            {
            }
            set
            {
            }
        }
        public override bool TrySkipIisCustomErrors
        {
            get
            {
            }
            set
            {
            }
        }
        public HttpResponseWrapper(HttpResponse httpResponse)
        {
        }
        public override void AddCacheItemDependency(string cacheKey)
        {
        }
        public override void AddCacheItemDependencies(ArrayList cacheKeys)
        {
        }
        public override void AddCacheItemDependencies(string[] cacheKeys)
        {
        }
        public override void AddCacheDependency(params CacheDependency[] dependencies)
        {
        }
        public override void AddFileDependency(string filename)
        {
        }
        public override void AddFileDependencies(ArrayList filenames)
        {
        }
        public override void AddFileDependencies(string[] filenames)
        {
        }
        public override void AddHeader(string name, string value)
        {
        }
        public override void AppendCookie(HttpCookie cookie)
        {
        }
        public override void AppendHeader(string name, string value)
        {
        }
        public override void AppendToLog(string param)
        {
        }
        public override string ApplyAppPathModifier(string virtualPath)
        {
        }
        public override IAsyncResult BeginFlush(AsyncCallback callback, object state)
        {
        }
        public override void BinaryWrite(byte[] buffer)
        {
        }
        public override void Clear()
        {
        }
        public override void ClearContent()
        {
        }
        public override void ClearHeaders()
        {
        }
        public override void Close()
        {
        }
        public override void DisableKernelCache()
        {
        }
        public override void DisableUserCache()
        {
        }
        public override void End()
        {
        }
        public override void EndFlush(IAsyncResult asyncResult)
        {
        }
        public override void Flush()
        {
        }
        public override void Pics(string value)
        {
        }
        public override void Redirect(string url)
        {
        }
        public override void Redirect(string url, bool endResponse)
        {
        }
        public override void RedirectPermanent(string url)
        {
        }
        public override void RedirectPermanent(string url, bool endResponse)
        {
        }
        public override void RedirectToRoute(object routeValues)
        {
        }
        public override void RedirectToRoute(string routeName)
        {
        }
        public override void RedirectToRoute(RouteValueDictionary routeValues)
        {
        }
        public override void RedirectToRoute(string routeName, object routeValues)
        {
        }
        public override void RedirectToRoute(string routeName, RouteValueDictionary routeValues)
        {
        }
        public override void RedirectToRoutePermanent(object routeValues)
        {
        }
        public override void RedirectToRoutePermanent(string routeName)
        {
        }
        public override void RedirectToRoutePermanent(RouteValueDictionary routeValues)
        {
        }
        public override void RedirectToRoutePermanent(string routeName, object routeValues)
        {
        }
        public override void RedirectToRoutePermanent(string routeName, RouteValueDictionary routeValues)
        {
        }
        public override void RemoveOutputCacheItem(string path)
        {
        }
        public override void RemoveOutputCacheItem(string path, string providerName)
        {
        }
        public override void SetCookie(HttpCookie cookie)
        {
        }
        public override void TransmitFile(string filename)
        {
        }
        public override void TransmitFile(string filename, long offset, long length)
        {
        }
        public override void Write(string s)
        {
        }
        public override void Write(char ch)
        {
        }
        public override void Write(char[] buffer, int index, int count)
        {
        }
        public override void Write(object obj)
        {
        }
        public override void WriteFile(string filename)
        {
        }
        public override void WriteFile(string filename, bool readIntoMemory)
        {
        }
        public override void WriteFile(string filename, long offset, long size)
        {
        }
        public override void WriteFile(IntPtr fileHandle, long offset, long size)
        {
        }
        public override void WriteSubstitution(HttpResponseSubstitutionCallback callback)
        {
        }
    }
}

光从代码本身的角度来说，可以说这个类什么事情也没做，但是它为我们提供了一个抽象体系（从抽象类HttpResponseBase继承），这样的话，我们的客户端代码就可以改写为：

protected HttpResponseBase _response;
protected void Page_Load(object sender, EvengArgs e)

{

_response.Write("test u");

}

OK，可测试了，因为我们可以在某个地方注入依赖给_response了。

注意，包装类的撰写，还可以使用接口，或者干脆也仅仅只是一个类，只要让被包装的这个同名的方法是virtual的就可以了。

另外，不可测试的那些类，可能往往已经作为稳定版本提交给客户了，我们就不能修改源代码然后告诉客户说你替换下我们的DLL吧，所以，为了让客户端程序员找到我们的包装类，可以让包装类以及被包装的类使用同一个命名空间。 

原文地址：https://www.cnblogs.com/luminji/archive/2012/12/31/2840455.html?utm_source=tuicool&utm_medium=referral