我们在开发WEB项目的时候，一般应用逻辑跟ASPX页面是分离的项目。应用逻辑一般会是一个DLL组件项目。如果这个组件项目中A方法使用了Session、Cookie等信息的读写，则这个方法就很难写单元测试。
但并不是写不出来，要写出来大致思路如下：
目标：
构建一个测试的环境，把需要的Session、Cookie等信息初始化好。 这样才好做测试。而且这个构建的环境，不应该影响实际功能代码的编写。
具体实现来说：
我们要使用Mock技术，但就HttpContext来言，直接mock这个对象会有一个问题，它不具备Session的功能。这时候我们就需要用 Mock 技术来构造一个可以满足我们需要的环境的原理：这个Mock的机制如下：
用反射机制，构造一个 HttpSessionState 对象（HttpSessionState类的构造函数是internal 的），然后把这个对象跟SimpleWorkerRequest 对象捆绑。
这样我们就可以 构建了一个满足自己需要的环境了，即 TestHttpContext 类。
以下是两个类的实现：
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web.SessionState;
using System.Web;
using System.Threading;
using System.Globalization;
using System.Collections.Specialized;
using System.Collections;
using System.IO;
using System.Web.Hosting;
using System.Reflection;
namespace TestNamespace
{
public class TestHttpContext
{
private const string ContextKeyAspSession = "AspSession";
private HttpContext context = null;
private TestHttpContext() : base() { }
public TestHttpContext(bool isSecure)
: this()
{
MySessionState myState = new MySessionState(Guid.NewGuid().ToString("N"),
new SessionStateItemCollection(), new HttpStaticObjectsCollection(),
5, true, HttpCookieMode.UseUri, SessionStateMode.InProc, false);
TextWriter tw = new StringWriter();
HttpWorkerRequest wr = new SimpleWorkerRequest("/webapp", "c:\\inetpub\\wwwroot\\webapp\\", "default.aspx", "", tw);
this.context = new HttpContext(wr);
HttpSessionState state = Activator.CreateInstance(
typeof(HttpSessionState),
BindingFlags.Public | BindingFlags.NonPublic |
BindingFlags.Instance | BindingFlags.CreateInstance,
null,
new object[] { myState },
CultureInfo.CurrentCulture) as HttpSessionState;
this.context.Items[ContextKeyAspSession] = state;
HttpContext.Current = this.context;
}
public HttpContext Context
{
get
{
return this.context;
}
}
private class WorkerRequest : SimpleWorkerRequest
{
private bool isSecure = false;
public WorkerRequest(string page, string query, TextWriter output, bool isSecure)
: base(page, query, output)
{
this.isSecure = isSecure;
}
public override bool IsSecure()
{
return this.isSecure;
}
}
}
public sealed class MySessionState : IHttpSessionState
{
const int MAX_TIMEOUT = 24 * 60; // Timeout cannot exceed 24 hours.
string pId;
ISessionStateItemCollection pSessionItems;
HttpStaticObjectsCollection pStaticObjects;
int pTimeout;
bool pNewSession;
HttpCookieMode pCookieMode;
SessionStateMode pMode;
bool pAbandon;
bool pIsReadonly;
public MySessionState(string id,
ISessionStateItemCollection sessionItems,
HttpStaticObjectsCollection staticObjects,
int timeout,
bool newSession,
HttpCookieMode cookieMode,
SessionStateMode mode,
bool isReadonly)
{
pId = id;
pSessionItems = sessionItems;
pStaticObjects = staticObjects;
pTimeout = timeout;
pNewSession = newSession;
pCookieMode = cookieMode;
pMode = mode;
pIsReadonly = isReadonly;
}
public int Timeout
{
get { return pTimeout; }
set
{
if (value <= 0)
throw new ArgumentException("Timeout value must be greater than zero.");
if (value > MAX_TIMEOUT)
throw new ArgumentException("Timout cannot be greater than " + MAX_TIMEOUT.ToString());
pTimeout = value;
}
}
public string SessionID
{
get { return pId; }
}
public bool IsNewSession
{
get { return pNewSession; }
}
public SessionStateMode Mode
{
get { return pMode; }
}
public bool IsCookieless
{
get { return CookieMode == HttpCookieMode.UseUri; }
}
public HttpCookieMode CookieMode
{
get { return pCookieMode; }
}
//
// Abandon marks the session as abandoned. The IsAbandoned property is used by the
// session state module to perform the abandon work during the ReleaseRequestState event.
//
public void Abandon()
{
pAbandon = true;
}
public bool IsAbandoned
{
get { return pAbandon; }
}
//
// Session.LCID exists only to support legacy ASP compatibility. ASP.NET developers should use
// Page.LCID instead.
//
public int LCID
{
get { return Thread.CurrentThread.CurrentCulture.LCID; }
set { Thread.CurrentThread.CurrentCulture = CultureInfo.ReadOnly(new CultureInfo(value)); }
}
//
// Session.CodePage exists only to support legacy ASP compatibility. ASP.NET developers should use
// Response.ContentEncoding instead.
//
public int CodePage
{
get
{
if (HttpContext.Current != null)
return HttpContext.Current.Response.ContentEncoding.CodePage;
else
return Encoding.Default.CodePage;
}
set
{
if (HttpContext.Current != null)
HttpContext.Current.Response.ContentEncoding = Encoding.GetEncoding(value);
}
}
public HttpStaticObjectsCollection StaticObjects
{
get { return pStaticObjects; }
}
public object this[string name]
{
get { return pSessionItems[name]; }
set { pSessionItems[name] = value; }
}
public object this[int index]
{
get { return pSessionItems[index]; }
set { pSessionItems[index] = value; }
}
public void Add(string name, object value)
{
pSessionItems[name] = value;
}
public void Remove(string name)
{
pSessionItems.Remove(name);
}
public void RemoveAt(int index)
{
pSessionItems.RemoveAt(index);
}
public void Clear()
{
pSessionItems.Clear();
}
public void RemoveAll()
{
Clear();
}
public int Count
{
get { return pSessionItems.Count; }
}
public NameObjectCollectionBase.KeysCollection Keys
{
get { return pSessionItems.Keys; }
}
public IEnumerator GetEnumerator()
{
return pSessionItems.GetEnumerator();
}
public void CopyTo(Array items, int index)
{
foreach (object o in items)
items.SetValue(o, index++);
}
public object SyncRoot
{
get { return this; }
}
public bool IsReadOnly
{
get { return pIsReadonly; }
}
public bool IsSynchronized
{
get { return false; }
}
}
}
这样我们在进行单元测试时就可以Mock掉Web下的Session,Cookie等对象。
例如：
public void TestGetUserId()
{
TestHttpContext mock = new TestHttpContext(false);
System.Web.HttpContext context = mock.Context;
context.Session["UserId"] = 1245;
Assert.AreEqual(long.Parse(context.Session["UserId"].ToString()), 1245, "读取用户ID错误！");
}