自定义AutoFixture以创建特定类型

Question

I want to create customization for NLog's LogLevel type. Instances can be created by FromOrdinal static method.

I want to restrict the ordinals used to create to the range (0..5). Please mind, that I don't want to customize the entire fixture with the generator (as other integers might be bigger).

Here's the piece of code that I tried to use:

class NLogCustomization : ICustomization
    {
        public void Customize(IFixture fixture)
        {
            fixture.Customize<NLog.LogLevel>(
                c => c.FromFactory(() =>
                    {
                        var ordinal = this.nlogOrdinalLevelFactory.Create<int>(); //Throws invalid cast exception
                        return NLog.LogLevel.FromOrdinal((int)ordinal);
                    }));
        }

        private readonly ISpecimenBuilder nlogOrdinalLevelFactory = new RandomNumericSequenceGenerator(0,5);
    }

Unfortunately the code above throws InvalidCastException. What am I doing wrong in here?

I'm using version 3.19.1.

Answer 1

To consume the RandomNumericSequenceGenerator and any other ISpecimenBuilder directly, use the ISpecimenBuilder interface:

object Create(object request, ISpecimenContext context);

In this example, instead of Create<T> do:

fixture.Customize<LogLevel>(c => c.FromFactory(() =>
{
    var ordinal = this.nlogOrdinalLevelFactory
        .Create(typeof(int), new SpecimenContext(fixture));

    return NLog.LogLevel.FromOrdinal((int)ordinal);
}));