【IT168技术文档】

  可能你已发现一个问题,我们无法使用VS对WPF项目创建单元测试(VS2005不行,VS2008我没试过,但据说也不行),这让人很郁闷,这里将介绍如何使用NUnit来对WPF项目创建单元测试并解决其中的难题(但利用NUnit来对WPF创建单元测试时并不会像针对.Net2.0一样容易，可能会出现一些小问题).

  1,对普通类（非WPF UI组件）进行测试：
  这和在.Net2.0中使用NUnit进行测试时一样，不会出现任何问题，参考下面的代码:

    [TestFixture]
public class ClassTest
{
[Test]
public void TestRun()
{
ClassLibrary1.Class1 obj = new ClassLibrary1.Class1();
double expected = 9;
double result = obj.GetSomeValue(3);
Assert.AreEqual(expected, result);
}
}

  2,对WPF UI组件进行测试
  使用NUnit对WPF UI组件（比如MyWindow，MyUserControl）进行测试的时候，NUnit会报如下异常：“The calling thread must be STA, because many UI components require this”。
  下面是错误的测试代码:

[TestFixture]
public class ClassTest
{
[Test]
public void TestRun()
{
WindowsApplication1.Window1 obj = new WindowsApplication1.Window1();
double expected = 9;
double result = obj.GetSomeValue(3);
Assert.AreEqual(expected, result);
}
}

  为了让调用线程为STA，我们可以编写一个辅助类CrossThreadTestRunner:

using System;
using System.Collections.Generic;
using System.Text;
using System.Threading;
using System.Security.Permissions;
using System.Reflection;
namespace TestUnit
{
public class CrossThreadTestRunner
{
private Exception lastException;
public void RunInMTA(ThreadStart userDelegate)
{
Run(userDelegate, ApartmentState.MTA);
}
public void RunInSTA(ThreadStart userDelegate)
{
Run(userDelegate, ApartmentState.STA);
}
private void Run(ThreadStart userDelegate, ApartmentState apartmentState)
{
lastException = null;
Thread thread = new Thread(
delegate()
{
try
{
userDelegate.Invoke();
}
catch (Exception e)
{
lastException = e;
}
});
thread.SetApartmentState(apartmentState);
thread.Start();
thread.Join();
if (ExceptionWasThrown())
ThrowExceptionPreservingStack(lastException);
}
private bool ExceptionWasThrown()
{
return lastException != null;
}
[ReflectionPermission(SecurityAction.Demand)]
private static void ThrowExceptionPreservingStack(Exception exception)
{
FieldInfo remoteStackTraceString = typeof(Exception).GetField(
"_remoteStackTraceString",
BindingFlags.Instance | BindingFlags.NonPublic);
remoteStackTraceString.SetValue(exception, exception.StackTrace + Environment.NewLine);
throw exception;
}
}
}