AutoFixture.AutoMoq supply a known value for one constructor parameter

Question

I\'ve just started to use AutoFixture.AutoMoq in my unit tests and I\'m finding it very helpful for creating objects where I don\'t care about the specific

Answer 1

You could do something like this. Imagine that you want to assign a particular value to the TimeSpan argument called lifespan.

public class LifespanArg : ISpecimenBuilder
{
    private readonly TimeSpan lifespan;

    public LifespanArg(TimeSpan lifespan)
    {
        this.lifespan = lifespan;
    }

    public object Create(object request, ISpecimenContext context)
    {
        var pi = request as ParameterInfo;
        if (pi == null)
            return new NoSpecimen(request);

        if (pi.ParameterType != typeof(TimeSpan) ||
            pi.Name != "lifespan")   
            return new NoSpecimen(request);

        return this.lifespan;
    }
}

Imperatively, it could be used like this:

var fixture = new Fixture();
fixture.Customizations.Add(new LifespanArg(mySpecialLifespanValue));

var sut = fixture.Create();

This approach can be generalized to some degree, but in the end, we're limited by the lack of a strongly typed way to extract a ParameterInfo from a particular constructor or method argument.