我有一些单元测试,期望“当前时间”与DateTime不同。显然,我不想改变电脑的时间。
实现这一目标的最佳策略是什么?
我有一些单元测试,期望“当前时间”与DateTime不同。显然,我不想改变电脑的时间。
实现这一目标的最佳策略是什么?
当前回答
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
其他回答
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;
}
}
以下是我对这个问题的回答。我将“环境上下文”模式与IDisposable结合起来。你可以使用DateTimeProvider。当前在您的正常程序代码和测试中,您使用using语句覆盖范围。
using System;
using System.Collections.Immutable;
namespace ambientcontext {
public abstract class DateTimeProvider : IDisposable
{
private static ImmutableStack<DateTimeProvider> stack = ImmutableStack<DateTimeProvider>.Empty.Push(new DefaultDateTimeProvider());
protected DateTimeProvider()
{
if (this.GetType() != typeof(DefaultDateTimeProvider))
stack = stack.Push(this);
}
public static DateTimeProvider Current => stack.Peek();
public abstract DateTime Today { get; }
public abstract DateTime Now {get; }
public void Dispose()
{
if (this.GetType() != typeof(DefaultDateTimeProvider))
stack = stack.Pop();
}
// Not visible Default Implementation
private class DefaultDateTimeProvider : DateTimeProvider {
public override DateTime Today => DateTime.Today;
public override DateTime Now => DateTime.Now;
}
}
}
下面是如何在单元测试中使用上述DateTimeProvider
using System;
using Xunit;
namespace ambientcontext
{
public class TestDateTimeProvider
{
[Fact]
public void TestDateTime()
{
var actual = DateTimeProvider.Current.Today;
var expected = DateTime.Today;
Assert.Equal<DateTime>(expected, actual);
using (new MyDateTimeProvider(new DateTime(2012,12,21)))
{
Assert.Equal(2012, DateTimeProvider.Current.Today.Year);
using (new MyDateTimeProvider(new DateTime(1984,4,4)))
{
Assert.Equal(1984, DateTimeProvider.Current.Today.Year);
}
Assert.Equal(2012, DateTimeProvider.Current.Today.Year);
}
// Fall-Back to Default DateTimeProvider
Assert.Equal<int>(expected.Year, DateTimeProvider.Current.Today.Year);
}
private class MyDateTimeProvider : DateTimeProvider
{
private readonly DateTime dateTime;
public MyDateTimeProvider(DateTime dateTime):base()
{
this.dateTime = dateTime;
}
public override DateTime Today => this.dateTime.Date;
public override DateTime Now => this.dateTime;
}
}
}
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。
我们使用的是静态SystemTime对象,但是在运行并行单元测试时遇到了问题。我尝试使用Henk van Boeijen的解决方案,但在派生异步线程上有问题,最终以类似于下面的方式使用AsyncLocal:
public static class Clock
{
private static Func<DateTime> _utcNow = () => DateTime.UtcNow;
static AsyncLocal<Func<DateTime>> _override = new AsyncLocal<Func<DateTime>>();
public static DateTime UtcNow => (_override.Value ?? _utcNow)();
public static void Set(Func<DateTime> func)
{
_override.Value = func;
}
public static void Reset()
{
_override.Value = null;
}
}
来源:https://gist.github.com/CraftyFella/42f459f7687b0b8b268fc311e6b4af08
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();
}