使用ThreadLocal<T>的线程安全SystemClock非常适合我。

ThreadLocal<T>在. net Framework v4.0及更高版本中可用。

/// <summary>
/// Provides access to system time while allowing it to be set to a fixed <see cref="DateTime"/> value.
/// </summary>
/// <remarks>
/// This class is thread safe.
/// </remarks>
public static class SystemClock
{
    private static readonly ThreadLocal<Func<DateTime>> _getTime =
        new ThreadLocal<Func<DateTime>>(() => () => DateTime.Now);

    /// <inheritdoc cref="DateTime.Today"/>
    public static DateTime Today
    {
        get { return _getTime.Value().Date; }
    }

    /// <inheritdoc cref="DateTime.Now"/>
    public static DateTime Now
    {
        get { return _getTime.Value(); }
    }

    /// <inheritdoc cref="DateTime.UtcNow"/>
    public static DateTime UtcNow
    {
        get { return _getTime.Value().ToUniversalTime(); }
    }

    /// <summary>
    /// Sets a fixed (deterministic) time for the current thread to return by <see cref="SystemClock"/>.
    /// </summary>
    public static void Set(DateTime time)
    {
        if (time.Kind != DateTimeKind.Local)
            time = time.ToLocalTime();

        _getTime.Value = () => time;
    }

    /// <summary>
    /// Resets <see cref="SystemClock"/> to return the current <see cref="DateTime.Now"/>.
    /// </summary>
    public static void Reset()
    {
        _getTime.Value = () => DateTime.Now;
    }
}

使用的例子:

[TestMethod]
public void Today()
{
    SystemClock.Set(new DateTime(2015, 4, 3));

    DateTime expectedDay = new DateTime(2015, 4, 2);
    DateTime yesterday = SystemClock.Today.AddDays(-1D);
    Assert.AreEqual(expectedDay, yesterday);

    SystemClock.Reset();
}

模拟对象。

一个模拟DateTime，返回适合您的测试的Now。

我也有同样的问题，但我在想我们不应该在同一类上使用设置日期时间的东西。因为有一天可能会导致滥用。我使用了提供商

public class DateTimeProvider
{
    protected static DateTime? DateTimeNow;
    protected static DateTime? DateTimeUtcNow;

    public DateTime Now
    {
        get
        {
            return DateTimeNow ?? System.DateTime.Now;
        }
    }

    public DateTime UtcNow
    {
        get
        {
            return DateTimeUtcNow ?? System.DateTime.UtcNow;
        }
    }

    public static DateTimeProvider DateTime
    {
        get
        {
            return new DateTimeProvider();
        }
    }

    protected DateTimeProvider()
    {       
    }
}

对于测试，在测试项目中创建了一个助手来处理设置的事情，

public class MockDateTimeProvider : DateTimeProvider
{
    public static void SetNow(DateTime now)
    {
        DateTimeNow = now;
    }

    public static void SetUtcNow(DateTime utc)
    {
        DateTimeUtcNow = utc;
    }

    public static void RestoreAsDefault()
    {
        DateTimeNow = null;
        DateTimeUtcNow = null;
    }
}

在代码

var dateTimeNow = DateTimeProvider.DateTime.Now         //not DateTime.Now
var dateTimeUtcNow = DateTimeProvider.DateTime.UtcNow   //not DateTime.UtcNow

在测试中

[Test]
public void Mocked_Now()
{
    DateTime now = DateTime.Now;
    MockDateTimeProvider.SetNow(now);    //set to mock
    Assert.AreEqual(now, DateTimeProvider.DateTime.Now);
    Assert.AreNotEqual(now, DateTimeProvider.DateTime.UtcNow);
}

[Test]
public void Mocked_UtcNow()
{
    DateTime utcNow = DateTime.UtcNow;
    MockDateTimeProvider.SetUtcNow(utcNow);   //set to mock
    Assert.AreEqual(utcNow, DateTimeProvider.DateTime.UtcNow);
    Assert.AreNotEqual(utcNow, DateTimeProvider.DateTime.Now);
}

但需要记住一件事，有时真正的DateTime和提供程序的DateTime并不相同

[Test]
public void Now()
{
    Assert.AreEqual(DateTime.Now.Kind, DateTimeProvider.DateTime.Now.Kind);
    Assert.LessOrEqual(DateTime.Now, DateTimeProvider.DateTime.Now);
    Assert.LessOrEqual(DateTimeProvider.DateTime.Now - DateTime.Now, TimeSpan.FromMilliseconds(1));
}

我假设差异是maximum TimeSpan.FromMilliseconds(0.00002)。但大多数时候甚至更少

在MockSamples中找到样本

我也遇到过同样的问题，但我发现微软的一个研究项目解决了这个问题。

http://research.microsoft.com/en-us/projects/moles/

mole是一个基于委托的。net测试存根和弯路的轻量级框架。mole可以用来绕过任何.NET方法，包括密封类型中的非虚拟/静态方法

// Let's detour DateTime.Now
MDateTime.NowGet = () => new DateTime(2000,1, 1);

if (DateTime.Now == new DateTime(2000, 1, 1);
{
    throw new Exception("Wahoo we did it!");
}

示例代码是在原始代码的基础上修改的。

我已经按照其他人的建议做了，并将DateTime抽象为一个提供程序。这感觉不对，我觉得光是测试就做不下去了。今晚我将把这个应用到我的个人项目中。

下面的代码为我工作:

  bizDeedMock.Verify(p => p.SetDeed(It.Is<DsPostList>(x => x.PostLists[0].registerDate.Year == DateTime.Now.Year)));
            bizDeedMock.Verify(p => p.SetDeed(It.Is<DsPostList>(x => x.PostLists[0].registerDate.Month == DateTime.Now.Month)));
            bizDeedMock.Verify(p => p.SetDeed(It.Is<DsPostList>(x => x.PostLists[0].registerDate.Day == DateTime.Now.Day)));

最好的策略是将当前时间封装在一个抽象中，并将该抽象注入到使用者中。

或者，你也可以将时间抽象定义为环境上下文:

public abstract class TimeProvider
{
    private static TimeProvider current =
        DefaultTimeProvider.Instance;

    public static TimeProvider Current
    {
       get { return TimeProvider.current; }
       set 
       {
           if (value == null)
           {
               throw new ArgumentNullException("value");
           }
           TimeProvider.current = value; 
       }
   }

   public abstract DateTime UtcNow { get; }

   public static void ResetToDefault()
   {    
       TimeProvider.current = DefaultTimeProvider.Instance;
   }            
}

这将使你能够像这样消费它:

var now = TimeProvider.Current.UtcNow;

在单元测试中，您可以替换TimeProvider。当前带有Test Double/Mock对象。使用Moq的例子:

var timeMock = new Mock<TimeProvider>();
timeMock.SetupGet(tp => tp.UtcNow).Returns(new DateTime(2010, 3, 11));
TimeProvider.Current = timeMock.Object;

但是，当使用静态状态进行单元测试时，始终记得通过调用TimeProvider.ResetToDefault()来删除fixture。