如何在单元测试中模拟夏令时转换？

Question

我有一个代码,用于比较上一个时间戳和实际时间戳.如果实际时间戳在最后一个时间戳之前,则系统时间已被操纵.由于从夏令时过渡到夏令时,我使用UTC.
现在我想为这种特殊情况编写单元测试.

public void TransitionFromDSTToNonDST()
{
    var dayLightChangeEnd= TimeZone.CurrentTimeZone.GetDaylightChanges(DateTime.Now.Year).End;
    var stillInDaylightSavingTime= dayLightChangeEnd.Subtract(TimeSpan.FromMinutes(62));
    //stillInDaylightSavingTime.IsDaylightSavingTime() returns true
    //stillInDaylightSavingTime is 01.58 am
    var noDaylightSavingTimeAnymore= dayLightChangeEnd.Subtract(TimeSpan.FromMinutes(32));
    //noDaylightSavingTimeAnymore.IsDaylightSavingTime() returns false
    //noDaylightSavingTimeAnymore is 02.28 am
}

但实际上我想模拟以下内容:

var stillInDaylightSavingTime = //for example 02.18 am BEFORE switching to Non-DST
var noDaylightSavingTimeAnymore = //for example 02.10 am AFTER switching to Non-DST

所以问题是如何定义02.18 am是否为DST.

Answer 1

MSDN说：

时区之间的转换操作（例如 UTC 与本地时间之间，或一个时区与另一个时区之间）会考虑夏令时，但算术和比较操作则不会。

IMO 您应该以 UTC 格式添加分钟数，然后转换为本地时间。

这是（更新后的）代码：

var dayLightChangeEnd = TimeZone.CurrentTimeZone.GetDaylightChanges(DateTime.Now.Year).End.ToUniversalTime();
var stillInDaylightSavingTime = dayLightChangeEnd.Subtract(TimeSpan.FromMinutes(62)).ToLocalTime();
Console.WriteLine(stillInDaylightSavingTime);
Console.WriteLine(stillInDaylightSavingTime.IsDaylightSavingTime());
var noDaylightSavingTimeAnymore = dayLightChangeEnd.Subtract(TimeSpan.FromMinutes(2)).ToLocalTime();
Console.WriteLine(noDaylightSavingTimeAnymore);
Console.WriteLine(noDaylightSavingTimeAnymore.IsDaylightSavingTime());

@WaltiD：我无法发表评论，但上面的代码在 DST 转换之前和之后打印 02:58。