New in .NET 8.0 [17]: Time abstraction for tests with time specifications

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In the base class library, Microsoft .NET 8.0 has added the abstract class TimeProvider, a simple way to simulate time information, including the time zone, as part of tests.

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Many developers have already written an abstraction for the current time instead of using System.DateTime.Now, System.DateTime.UtcNow and System.DateTimeOffset.Now, because real unit tests for program code that depend on the time or date is, needs an abstraction. Otherwise you would have to wait until a certain time or date to start the tests.

Microsoft now provides a built-in abstraction in .NET 8.0. The time specifications in Task.Delay() and Task.Async() can also use this.

The following listing shows several aspects:

TimeProvider.System returns a TimeProvider with the real time according to the system clock.FakeTimeProvider is a class from Microsoft that is supplied in the NuGet package Microsoft.Extensions.TimeProvider.Testing. This class allows a fixed time specification, which can be introduced manually with Advance() by specifying a TimeSpan object or with each readout, for example fakeTime.AutoAdvanceAmount = TimeSpan.FromHours(1). class FCL_TimeProvider { public async Task Run() { void PrintTime(TimeProvider timeProvider) { Console.Write(“Local time: ” + timeProvider.GetLocalNow()); Console.WriteLine(” | UTC: ” + timeProvider.GetUtcNow()); } void Callback(TimeProvider timeProvider) { Console.WriteLine(“Time with ” + timeProvider.GetType()); PrintTime(timeProvider); } CUI.H2(“Regular system time”); PrintTime(TimeProvider.System); // // Microsoft.Extensions.TimeProvider.Testing/ CUI.H2(“Fake time time provider from “+ “Microsoft.Extensions.TimeProvider.Testing”); var fakeTime = new FakeTimeProvider(new(DateTime.Parse(“11/14/2023 6:00:00 PM”))); PrintTime(fakeTime); // November 14th, 2023 6 p.m. Console.WriteLine(“We are now setting the time forward 30 minutes”); fakeTime.Advance(TimeSpan.FromMinutes(30)); // November 14, 2023 6:30 p.m.: Console.WriteLine(“UTC: ” + fakeTime.GetUtcNow()); Console.WriteLine(“We advance the time by 1 hour each time we read ” + “the time”); fakeTime.AutoAdvanceAmount = TimeSpan.FromHours(1); // November 14, 2023 7:30 p.m.: Console.WriteLine(“UTC: ” + fakeTime.GetUtcNow()); // November 14, 2023 8:30 p.m.: Console.WriteLine(“UTC: ” + fakeTime.GetUtcNow()); // November 14, 2023 9:30 p.m.: Console.WriteLine(“UTC: ” + fakeTime.GetUtcNow()); async Task Wait5Seconds(TimeProvider t) { CUI.Cyan(“Waiting begins”); PrintTime(TimeProvider.System); await t.Delay(new TimeSpan(0, 0, 6)); // or //await Task.Delay(new TimeSpan(0, 0, 5), fakeTimeProvider); PrintTime(TimeProvider.System); CUI.Cyan(“Waiting finished!”); } CUI.H2(“6 seconds waiting for TimeProvider.System”); await Wait5Seconds(TimeProvider.System); CUI.H2(“6 seconds waiting for FakeTimeProvider from Microsoft”); var IncreaseTimeAfterOneSecondby10Seconds = async () => { await Task.Delay(new TimeSpan(0, 0, 1)); fakeTime.Advance(TimeSpan.FromSeconds(10)); }; #pragma warning disable CS4014 IncreaseTimeAfterOneSecondBy10Seconds(); #pragma warning restore CS4014 //–> this never ends if you don’t call Advance()!: await Wait5Seconds(fakeTime); } }

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