对包含HttpContext.Current.Cache的代码进行单元测试

假设我们如下代码调用了HttpContext.Current.Cache

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public class CacheManager {   public static HttpContext mHttpContext = HttpContext.Current;     public void SetCache<t>(string key, T value)   {      mHttpContext.Cache.Insert(key, value, null, DateTime.MaxValue, new TimeSpan(0, 100, 0));   }     public T GetCache<t>(string key)   {      return (T)mHttpContext.Cache.Get(key);   }   }</t></t>

现在我有一个类调用了上面的GetCache<T>

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public class LanguageController {     private CacheManager cacheManger = new CacheManager();         public string Get_UserLanguage()     {         string userLanguage=cacheManger.GetCache<string>("userLanguage");           if (!string.IsNullOrEmpty(userLanguage)) return userLanguage;           return "zh-CN";     }        }</string>

我们现在需要测LanguageController的Get_UserLanuage,写如下代码

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[TestMethod] public void Test_Get_UserLanguage() {     CacheManager cacheManger = new CacheManager();   cacheManger.SetCache<string>("userLanguage", "en-GB");     LanguageController languageController = new LanguageController();     Assert.AreEqual(languageController.Get_UserLanguage(), "en-GB");    }</string>

运行测试，失败，得到如下消息

System.NullReferenceException: Object reference not set to an instance of an object.

跟踪调试，发现下面方法这句mHttpContext.Cache为空

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public void SetCache<t>(string key, T value) {    mHttpContext.Cache.Insert(key, value, null, DateTime.MaxValue, new TimeSpan(0, 100, 0)); }</t>

现在，将测试代码改为如下：

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[TestMethod] public void Test_Get_Language_By_Fake() {   HttpContext.Current = new HttpContext(new HttpRequest(null,        "http://10.10.50.127/RGV2/devtest1", null), new HttpResponse(null));     CacheManager.mHttpContext = HttpContext.Current;     CacheManager cacheManger = new CacheManager();     cacheManger.SetCache<string>("userLanguage", "en-GB");     LanguageController languageController = new LanguageController();     Assert.AreEqual(languageController.Get_UserLanguage(), "en-GB");   }</string>

测试通过：

总结，当我们测试的包含HttpContext.Current.Cache代码时：

1. 将HttpContext.Current.Cache 公布为类的静态属性，这样测试时，一个地方改了，全部就改过来了

2. 用下面的代码来给HttpContext.Current赋值

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HttpContext.Current = new HttpContext(new HttpRequest(null,                         "http://10.10.50.127/RGV2/devtest1", null), new HttpResponse(null));   CacheManager.mHttpContext = HttpContext.Current;

3. 建议所有调用HttpContext获得值的地方，尽量公布为属性，这样方便测试,比如如下的代码我们就直接赋值了,这个和本文关系不大，只是一个实践而已。

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public class ConfigController  {     private string tempConfigPath;     public string mConfigPath     {         get         {             if (tempConfigPath == null)             {                 tempConfigPath = HttpContext.Current.Server.MapPath(@"~/App_Data/config.xml");             }             return tempConfigPath;         }         set         {             tempConfigPath = value;         }     } }

4. 我们也可以使用Mock，但是个人认为上面的方法更简单点。