背景
年龄大点的程序员都知道在vs2010中创建单元测试非常的简单，鼠标定位在方法名字，右键创建单元测试，就会创建一个测试方法，即使是在私有方法上也可以创建测试方法。
VS2010以后就没这么简单了，微软默认取消了这种快捷方式，安装 Unit Test Generator 插件也只能在公有方法上创建单元测试。为了方便的测试私有方法，我们需要一种反射调用私有成员的方法。这种现成的方法可以在网上找到不少，我这里是讲述如何从VS2010
的UnitTestFramework类库提取反射调用私有成员的方法。
VS2010私有方法单元测试分析
在vs2010里新建个测试类：
public class Class1
{
private string GetName(string name, int age)
{
return name + age;
}
}
Class1
创建单元测试
/// <summary>
///GetName 的测试
///</summary>
[TestMethod()]
[DeploymentItem("ClassLibrary1.dll")]
public void GetNameTest()
{
Class1_Accessor target = new Class1_Accessor(); // TODO: 初始化为适当的值
string name = string.Empty; // TODO: 初始化为适当的值
int age = ; // TODO: 初始化为适当的值
string expected = string.Empty; // TODO: 初始化为适当的值
string actual;
actual = target.GetName(name, age);
Assert.AreEqual(expected, actual);
Assert.Inconclusive("验证此测试方法的正确性。");
}
Class1 Test
有这么一行 [DeploymentItem("ClassLibrary1.dll")]，多了个 Class1_Accessor
使用ILSpy打开ClassLibrary1.dll看看
可以看出Class1_Accessor : BaseShadow ，实例化时调用了基类的构造方法，实例化一个privateObject并赋给了m_privateObject ，GetName方法就是调用了m_privateObject 的invoke获取返回值。
protected BaseShadow(PrivateObject privateTarget)
{
this.m_privateObject = privateTarget;
}
沿着 BaseShadow ->PrivateObject->PrivateType->RuntimeTypeHelper->Helper的顺序把相关的代码都保存下来，文章最后提供下载。
其中用到FrameworkMessages 的都是错误信息相关的，用到了资源文件。这里没有照搬而是把用到的几个信息敲了一遍，如下：
class FrameworkMessages
{
public static string PrivateAccessorMemberNotFound(string name)
{
return string.Format("The member specified ({0}) could not be found.You might need to regenerate your private accesscor the member may be private and defined on a base class." +
"If the latter is true,you need to pass the type that defines the member into PrivateObject's constructor", name);
} public static string AccessStringInvalidSyntax
{
get { return "Access string has invalid syntax."; }
} public static string PrivateAccessorConstructorNotFound
{
get { return "The constructor with the specified signature could not be found.You might need to regenerate your private accesscor the member may be private and defined on a base class." +
"If the latter is true,you need to pass the type that defines the member into PrivateObject's constructor"; }
} }
FrameworkMessages
用到的方法找齐了，写个测试用例，首先定义一个需要访问的类
public class DemoClass
{
public string Name { get; set; }
public int Age { get; set; }
public DemoClass():this("zeroes",)
{
} public DemoClass(string name, int age)
{
this.Name = name;
this.Age = age;
} private string PrivateMethod(DateTime time)
{
return "姓名:{0} 年龄:{1} 时间:{2}".FormatWith(this.Name, this.Age, time.ToString("yyyy"));
}
}
DemoClass
然后封装一个私有反射的帮助类
/// <summary>
/// 调用方法单元测试管理类
/// </summary>
public static class PrivateUnitTestUtil
{ /// <summary>
/// 调用私有方法
/// </summary>
/// <param name="t">要访问的类类型</param>
/// <param name="methodName">方法名字</param>
/// <param name="paras">参数</param>
/// <returns></returns>
public static object InvokeMethod(Type t, string methodName, params object[] paras)
{
var privateObject = new PrivateObject(t);
return privateObject.Invoke(methodName, paras);
} /// <summary>
/// 调用私有方法
/// </summary>
/// <param name="instance">要访问的类实例</param>
/// <param name="methodName">方法名字</param>
/// <param name="paras">参数</param>
/// <returns></returns>
public static object InvokeMethod(object instance, string methodName, params object[] paras)
{
var privateObject = new PrivateObject(instance);
return privateObject.Invoke(methodName, paras);
}
}
PrivateUnitTestUtil
在测试项目中调用
[TestClass]
public class PrivateUnitTestUtilTests
{
[TestMethod]
public void InvokeMethodTest()
{
var instance = new DemoClass();
instance.Name = "";
DateTime time = DateTime.Now;
var ret = (string) PrivateUnitTestUtil.InvokeMethod(instance, "PrivateMethod", time);
Assert.AreEqual(ret, "姓名:{0} 年龄:{1} 时间:{2}".FormatWith(instance.Name, instance.Age, time.Year));
}
}
PrivateUnitTestUtilTests
更多的调用方式可以慢慢补充，相关文件下载地址：http://download.csdn.net/detail/zbl131/9493247