Provides a testable abstraction and alternative to System.Threading.Timer, System.Timers.Timer and System.Threading.PeriodicTimer. Targets netstandard2.0 and higher.
As of the release of .Net 8 (nov. 14th 2023) Microsoft provides the TimeProvider class and ITimer interface. A good primer on this topic is over at Andrew Lock's site (archived version). You may want to check that out before continuing. What that means for ITimer? It'll most likely be the end of this library, but that's a good thing. I'll keep supporting it for a while but switching to the Microsoft provided solution shouldn't be too hard.
Timer related code is, or should I say used to be, hard to unittest. When you have timer related code, you (probably) don't want to wait until the timer elapses in your unittest which would in turn make your unittests slower than strictly necessary.
The basis for this library is the ISignaler interface which defines an interface for timers to implement that allow you to replace those timers with the TestTimer in your unittests so you have total control over when the timer fires the Elapsed event.
This library provides the most common timers: System.Threading.Timer, System.Timers.Timer and System.Threading.PeriodicTimer wrapped in the ThreadingTimer and SystemTimer classes respectively. Other, custom, timers should be simple to implement by simply implementing the ISignaler interface.
Agreed, ISignaler is not the best name. ITimer would have been a much better choice, but that conflicts with the namespace. That would require you to write ITimer.ITimer everywhere this interface is used. And since we wanted a simple package-ID and simple (root) namespace we opted for ITimer as namespace and ISignaler as interface name. If you have any better suggestions, please let us know and we'll consider it for the next major version.
In your code:
public class MyClass
{
private readonly ISignaler _timer;
public MyClass(ISignaler timer)
{
_timer = timer ?? throw new ArgumentNullException(nameof(timer));
_timer.Elapsed += (s, e) => {
// Do work here...
Console.WriteLine($"Tick tock! {e.SignalTime}");
};
}
public void Start() {
_timer.Start();
}
public void Stop() {
_timer.Stop();
}
}
using (var myTimer = new SystemTimer()) {
var myclass = new MyClass(myTimer);
myClass.Start();
//...
}Or, even better, using Dependency Injection:
public void ConfigureServices(IServiceCollection services)
{
// Register SystemTimer as ISignaler
services.AddScoped<ISignaler, SystemTimer>();
// ...
}For usage in unittests, see the TestTimer below.
The ISignaler interface defines the Start() and Stop() methods to start and stop the timer raise the Elapsed event. The Interval property gets the timer's interval and the AutoReset property returns whether or not the timer should fire the event once and then stop, or keep going in a fire event / wait cycle.
As mentioned before, these timers encapsulate (or "wrap") the System.Threading.Timer and System.Timers.Timer timers and provide a unified interface because they both implement the ISignaler interface. The difference between the first two is perhaps best explained by Jon Skeet (archived version here or here). The System.Windows.Forms.Timer is not provided by this library but should be simple to implement.
All timers provided by this library are simplified versions of the underlying timers unified to a single, simple, interface. If you need a more specific implementation then you may want to implement them again in your own class, also implementing the ISignaler interface.
With the TestTimer you are in complete control over when, and how often, the timer fires. You even control the SignalTime so you can specify at what (pretend) time the timer fired. Ofcourse, this is very useful in unittests.
The TestTimer offers some extra properties like the TickCount, StartCount and StopCount that keep track of how often the Elapsed event has been raised and the timer has been started and stopped respectively (all of which can be reset with the Reset() method). The Elapsed event for the TestTimer provides the TestTimerElapsedEventArgs which also contains a TickCount property.
Most important, however, for the TestTimer are the Tick(DateTimeOffset?), Tick(IEnumerable<DateTimeOffset>) and Tick(Int32, Func<Int32, DateTimeOffset>) methods. These methods will raise the Elapsed event on the TestTimer and allow you to specify the SignalTime.
Given the above example, we can now replace the SystemTimer with a TestTimer for our tests:
using (var myTestTimer = new TestTimer()) {
var myclass = new MyClass(myTestTimer);
myTestTimer.Tick(); // Raise elapsed event
Assert.IsTrue(...);
}The different overloads of the Tick() method allow you to raise the event multiple times. The TestTimer has a constructor argument requireStart that allows you to specify wether you require the timer to be started before it will start raising events or not; this defaults to the latter, making your unittests more concise not having to start the TestTimer each time. When this value equals true the event won't be raised by any of the Tick() methods unless Start() is called.
Licensed under MIT license. See LICENSE for details.
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