这些都是很好的答案，这是我在另一个项目中所做的:

用法:

获取今天的真实日期时间

var today = SystemTime.Now().Date;

而不是使用DateTime。现在，你需要使用SystemTime.Now()…这并不难改变，但这种解决方案可能并不适合所有项目。

时间旅行(让我们去5年后)

SystemTime.SetDateTime(today.AddYears(5));

获得我们虚假的“今天”(从“今天”开始算起5年)

var fakeToday = SystemTime.Now().Date;

重置日期

SystemTime.ResetDateTime();

/// <summary>
/// Used for getting DateTime.Now(), time is changeable for unit testing
/// </summary>
public static class SystemTime
{
    /// <summary> Normally this is a pass-through to DateTime.Now, but it can be overridden with SetDateTime( .. ) for testing or debugging.
    /// </summary>
    public static Func<DateTime> Now = () => DateTime.Now;

    /// <summary> Set time to return when SystemTime.Now() is called.
    /// </summary>
    public static void SetDateTime(DateTime dateTimeNow)
    {
        Now = () =>  dateTimeNow;
    }

    /// <summary> Resets SystemTime.Now() to return DateTime.Now.
    /// </summary>
    public static void ResetDateTime()
    {
        Now = () => DateTime.Now;
    }
}

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();
}

在使用ITimeProvider时，我们被迫将它作为一个特殊的共享项目，必须从其他项目中引用它。但这使得依赖关系的控制变得复杂。

我们在。net框架中搜索ITimeProvider。我们搜索了NuGet包，发现了一个不能使用DateTimeOffset的包。

所以我们提出了自己的解决方案，它只依赖于标准库的类型。我们正在使用Func<DateTimeOffset>的实例。

如何使用

public class ThingThatNeedsTimeProvider
{
    private readonly Func<DateTimeOffset> now;
    private int nextId;

    public ThingThatNeedsTimeProvider(Func<DateTimeOffset> now)
    {
        this.now = now;
        this.nextId = 1;
    }

    public (int Id, DateTimeOffset CreatedAt) MakeIllustratingTuple()
    {
        return (nextId++, now());
    }
}

如何注册

自发法克

builder.RegisterInstance<Func<DateTimeOffset>>(() => DateTimeOffset.Now);

(未来的编辑请在这里附上你的案例)。

如何进行单元测试

public void MakeIllustratingTuple_WhenCalled_FillsCreatedAt()
{
    DateTimeOffset expected = CreateRandomDateTimeOffset();
    DateTimeOffset StubNow() => expected;
    var thing = new ThingThatNeedsTimeProvider(StubNow);

    var (_, actual) = thing.MakeIllustratingTuple();

    Assert.AreEqual(expected, actual);
}

一种简单的方法是注入VirtualTime。它可以让你控制时间。 首先安装VirtualTime

Install-Package VirtualTime

例如，这允许在所有对DateTime的调用上使时间加快5倍。Now或UtcNow

var DateTime = DateTime.Now.ToVirtualTime(5);

放慢时间(如放慢5倍)

var DateTime = DateTime.Now.ToVirtualTime(0.5);

让时间静止

var DateTime = DateTime.Now.ToVirtualTime(0);

回到过去还没有测试过

下面是一个测试示例:

[TestMethod]
public void it_should_make_time_move_faster()
{
    int speedOfTimePerMs = 1000;
    int timeToPassMs = 3000;
    int expectedElapsedVirtualTime = speedOfTimePerMs * timeToPassMs;
    DateTime whenTimeStarts = DateTime.Now;
    ITime time = whenTimeStarts.ToVirtualTime(speedOfTimePerMs);
    Thread.Sleep(timeToPassMs);
    DateTime expectedTime = DateTime.Now.AddMilliseconds(expectedElapsedVirtualTime - timeToPassMs);
    DateTime virtualTime = time.Now;

    Assert.IsTrue(TestHelper.AreEqualWithinMarginOfError(expectedTime, virtualTime, MarginOfErrorMs));
}

你可以在这里查看更多测试:

https://github.com/VirtualTime/VirtualTime/blob/master/VirtualTimeLib.Tests/when_virtual_time_is_used.cs

什么DateTime.Now.ToVirtualTime扩展给你是一个ITime的实例，你传递给一个依赖于ITime的方法/类。一些DateTime.Now.ToVirtualTime被设置在你选择的DI容器中

下面是注入类构造函数的另一个例子

public class AlarmClock
{
    private ITime DateTime;
    public AlarmClock(ITime dateTime, int numberOfHours)
    {
        DateTime = dateTime;
        SetTime = DateTime.UtcNow.AddHours(numberOfHours);
        Task.Run(() =>
        {
            while (!IsAlarmOn)
            {
                IsAlarmOn = (SetTime - DateTime.UtcNow).TotalMilliseconds < 0;
            }
        });
    }
    public DateTime SetTime { get; set; }
    public bool IsAlarmOn { get; set; }
}

[TestMethod]
public void it_can_be_injected_as_a_dependency()
{
    //virtual time has to be 1000*3.75 faster to get to an hour 
    //in 1000 ms real time
    var dateTime = DateTime.Now.ToVirtualTime(1000 * 3.75);
    var numberOfHoursBeforeAlarmSounds = 1;
    var alarmClock = new AlarmClock(dateTime, numberOfHoursBeforeAlarmSounds);
    Assert.IsFalse(alarmClock.IsAlarmOn);
    System.Threading.Thread.Sleep(1000);
    Assert.IsTrue(alarmClock.IsAlarmOn);
}

你有一些选择:

使用模拟框架并使用DateTimeService(实现一个小型包装器类并将其注入到生产代码中)。包装器实现将访问DateTime，在测试中您将能够模拟包装器类。 使用Typemock隔离器，它可以伪造日期时间。现在，并且不需要您更改测试中的代码。 使用鼹鼠，它也可以伪造日期时间。现在，并且不需要更改生产代码。

一些例子:

使用Moq的包装器类:

[Test]
public void TestOfDateTime()
{
     var mock = new Mock<IDateTime>();
     mock.Setup(fake => fake.Now)
         .Returns(new DateTime(2000, 1, 1));

     var result = new UnderTest(mock.Object).CalculateSomethingBasedOnDate();
}

public class DateTimeWrapper : IDateTime
{
      public DateTime Now { get { return DateTime.Now; } }
}

直接使用隔离器伪造日期时间:

[Test]
public void TestOfDateTime()
{
     Isolate.WhenCalled(() => DateTime.Now).WillReturn(new DateTime(2000, 1, 1));

     var result = new UnderTest().CalculateSomethingBasedOnDate();
}

免责声明-我在Typemock工作

一个老问题，但仍然有效。

我的方法是创建一个新的接口和类来包装System.DateTime.Now调用

public interface INow
{
    DateTime Execute();
}

public sealed class Now : INow
{
    public DateTime Execute()
    {
        return DateTime.Now
    }
}

该接口可以注入到任何需要获取当前日期和时间的类中。在这个例子中，我有一个类，它将一个时间跨度添加到当前日期和时间(一个可测试的单元System.DateTime.Now.Add(timespan))

public interface IAddTimeSpanToCurrentDateAndTime
{
    DateTime Execute(TimeSpan input);
}

public class AddTimeSpanToCurrentDateAndTime : IAddTimeSpanToCurrentDateAndTime
{
    private readonly INow _now;

    public AddTimeSpanToCurrentDateAndTime(INow now)
    {
        this._now = now;
    }

    public DateTime Execute(TimeSpan input)
    {
        var currentDateAndTime = this._now.Execute();

        return currentDateAndTime.Add(input);
    }
}

并且可以编写测试以确保其正确运行。我使用NUnit和Moq，但任何测试框架都可以

public class Execute
{
    private Moq.Mock<INow> _nowMock;

    private AddTimeSpanToCurrentDateAndTime _systemUnderTest;

    [SetUp]
    public void Initialize()
    {
        this._nowMock = new Moq.Mock<INow>(Moq.MockBehavior.Strict);

        this._systemUnderTest = AddTimeSpanToCurrentDateAndTime(
            this._nowMock.Object);
    }

    [Test]
    public void AddTimeSpanToCurrentDateAndTimeExecute0001()
    {
        // arrange

        var input = new TimeSpan(911252);

        // arrange : mocks

        this._nowMock
            .Setup(a => a.Execute())
            .Returns(new DateTime(348756););

        // arrange : expected

        var expected = new DateTime(911252 + 348756);

        // act

        var actual = this._systemUnderTest.Execute(input).Result;

        // assert

        Assert.Equals(actual, expected);
    }
}

此模式适用于依赖于外部因素的任何函数，如System.Random.Next()， System.DateTime.Now。UtcNow, system . guide . newguid()等。

参见https://loadlimited.visualstudio.com/Stamina/_git/Stamina.Core获取更多示例或获取https://www.nuget.org/packages/Stamina.Core nuget包。