Substitute for Task<T>

[Steve Finn]

From looking around it looks as though it is possible to use NSubstitute to unit test in Async/Await scenario. I can't find any docs for the syntax.

I have a Repository that I would normally substitute in a sync context as follows:
Repository.FindFirstByPredicate<Device>(Arg.Any<Expression<Func<Device, bool>>>()).Returns(new Device{ blah = blah blah});

My repository now has a FindFirstByPredicateAsync<T> method, how would I substitute for that which of course returns Task<T> or Task<Device> using the above example.


Any assistance is truly appreciated.

Best regards,
Steve

[David Tchepak]

No special syntax; just return the task you want. For example:

public interface IRepository

{

    Task<T> FindFirst<T>(Func<T, bool> pred);

}

[Test]

public async Task Async()

{

    var repository = Substitute.For<IRepository>();

    repository.FindFirst(Arg.Any<Func<int, bool>>()).Returns(Task.FromResult(42));

    var result = await repository.FindFirst<int>(x => true);

    Assert.That(result, Is.EqualTo(42));

}

Please let me know if you run into any problems with this.

Regards,

David

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[Steve Finn]

David,

Many many thanks for your reply. I wasn't aware of Task.FromResult !

Once again thx for your help.

Steve