Time system

ITimeSystem wraps everything in the BCL that depends on the wall clock or makes a thread wait. Replace it with a MockTimeSystem in tests and you can fast-forward time without sleeping.

What it covers

Sub-property	Wraps
DateTime	DateTime.Now, DateTime.UtcNow, DateTime.Today (plus MinValue, MaxValue, UnixEpoch)
DateTimeOffset	DateTimeOffset.Now, DateTimeOffset.UtcNow (plus MinValue, MaxValue, UnixEpoch)
Stopwatch	System.Diagnostics.Stopwatch
Task	Task.Delay
Thread	Thread.Sleep
PeriodicTimer	System.Threading.PeriodicTimer (.NET 8 or later)
Timer	System.Threading.Timer
TimeZoneInfo	System.TimeZoneInfo (Local, Utc, FindSystemTimeZoneById, GetSystemTimeZones)

Implementations

Type	Package	Use it for
RealTimeSystem	Testably.Abstractions	Production
MockTimeSystem	Testably.Abstractions.Testing	Unit tests

ITimeSystem timeSystem = new MockTimeSystem();

// any Thread.Sleep / Task.Delay / Stopwatch / Timer call goes through this instance
timeSystem.Thread.Sleep(TimeSpan.FromMinutes(5));
DateTime now = timeSystem.DateTime.Now; // advanced by 5 minutes

In this section

📄️Configuring time

Choose the start time and the local time zone of the MockTimeSystem, plug in a custom time provider, or use it as a .NET TimeProvider.

📄️Auto-advance

How MockTimeSystem moves its clock when the code under test waits, and how to drive the clock yourself.

📄️Stopwatch

Measure simulated elapsed time with the mocked Stopwatch, independent of changes to the wall clock.

📄️Timer

Wait for a mocked System.Threading.Timer to fire a given number of times instead of sleeping.

📄️PeriodicTimer

Test loops built on PeriodicTimer without waiting for real time to pass.

📄️Notifications

Observe and wait for sleeps, delays, clock reads and timer ticks of the code under test.

📄️Thread-aware time provider

Give each async context its own simulated clock with a custom ITimeProvider.