c# - Mocking Task.Delay -

i have method following line: await task.delay(waittime).configureawait(false);

i there strategy avoid waiting few seconds when unit testing , instead verify tried wait specific number of seconds.

for instance, there way inject additional parameter method in (contrived) example inject mocked object of fictitious itaskwaiter interface:

// arrange var mockwait = new mock<itaskwaiter>(mockbehavior.strict); mockwait.setup(w => w.delay(it.is<timespan>(t => t.totalseconds == 2)));  // act myobject.mymethod(mockwait.object);  // assert mockwait.verify(); 

you can define "delayer" interface this:

public interface iasyncdelayer {     task delay(timespan timespan); } 

and can provide following implementation production code:

public class asyncdelayer : iasyncdelayer {     public task delay(timespan timespan)     {         return task.delay(timespan);     } } 

now, class this:

public class classundertest {     private readonly iasyncdelayer asyncdelayer;      public classundertest(iasyncdelayer asyncdelayer)     {         this.asyncdelayer = asyncdelayer;     }      public async task<int> methodundertest()     {         await asyncdelayer.delay(timespan.fromseconds(2));          return 5;     } } 

this basic application of dependency injection. basically, extracted logic of asynchronously waiting different class , created interface enable polymorphism.

in production, compose object this:

var myclass = new classundertest(new asyncdelayer()); 

now, in test can create fake delayer returns this:

[testmethod] public async task testmethod1() {     var mockwait = new mock<iasyncdelayer>();      mockwait.setup(m => m.delay(it.isany<timespan>())).returns(task.fromresult(0));      var sut = new classundertest(mockwait.object);      var result = await sut.methodundertest();      assert.areequal(5, result); }