paxdev / PaxDev.Machines.Fakes.Async

Helper classes to assist with async in Machine.Specifications

Overview

PaxDev.Machine.Fakes.Async is a library to help reduce boiler plate code associated with using Machine.Fakes method mocking with Task<T>.

To use simply reference the NuGet package and then write code like the following:

public interface ITestInterface
{
    Task<string> MethodWithTwoParameters(string parameter1, int parameter2);
}

public class When_testing_a_method_that_returns_a_task : WithFakes
{
    Establish context = () =>
        The<ITestInterface>()
            .WhenToldTo(d => d.MethodWithTwoParameters(Param<string>.IsAnything, Param<int>.IsAnything))
            .ReturnAsync((string s, int i) => DoFunction(s, i));

    static string DoFunction(string s, int i) => $"Do something with {s} and {i}";
}

You can, of course, inline the function declaration. Under the hood, the library will create a CompletedTask with the value of the function / return value.

This has an additional benefit when the Result type is polymorphic. .Net is able to infer the correct Task<T> from the method signature and cast the Result to the correct type.