Ninject ambiguous test

Chapter_9_ConstraintAttribute_Bindings.cs

using System;
using Ninject;
using Ninject.Planning.Bindings;

namespace NinjectExamples
{
    using Xunit;
    using Xunit.Should;

    public class Chapter_9_ConstraintAttribute_Bindings
    {
        [Fact]
        public void CanUseContraintAttributes()
        {
            var kernel = new StandardKernel();
            kernel.Bind<IWarrior>().To<Ninja>();
            kernel.Bind<IWarrior>().To<Samurai>().WithMetadata("CanSwim", false);
            kernel.Bind<IWarrior>().To<SpecialNinja>().WithMetadata("CanSwim", true);

            kernel.Get<AmbiguiousAttack>().Warrior.ShouldBeInstanceOf<SpecialNinja>();
        }

        [Fact]
        public void IfNoAttributeProvidedWillResolveToFirstBinding()
        {
            var kernel = new StandardKernel();
            kernel.Bind<IWarrior>().To<Samurai>().WithMetadata("CanSwim", false);
            kernel.Bind<IWarrior>().To<SpecialNinja>().WithMetadata("CanSwim", true);

            kernel.Get<AmbiguiousAttack>().Warrior.ShouldBeInstanceOf<Samurai>();
        }

        public interface IWarrior { }
        public class Ninja : IWarrior { }

        public class Samurai : IWarrior { }
        public class SpecialNinja : IWarrior { }

        private class AmbiguiousAttack
        {
            public IWarrior Warrior;

            public AmbiguiousAttack(IWarrior warrior)
            {
                Warrior = warrior;
            }
        }

        private class AmphibiousAttack
        {
            public IWarrior Warrior;

            public AmphibiousAttack([Swimmer]IWarrior warrior)
            {
                Warrior = warrior;
            }
        }

        [AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = true, Inherited = true)]
        private class Swimmer : ConstraintAttribute
        {
            public override bool Matches(IBindingMetadata metadata)
            {
                return metadata.Has("CanSwim") && metadata.Get<bool>("CanSwim");
            }
        }
    }
}

Test_Failure.txt

Chapter_9_ConstraintAttribute_Bindings.IfNoAttributeProvidedWillResolveToFirstBinding : FailedNinject.ActivationException: Error activating IWarrior
More than one matching bindings are available.
Activation path:
  2) Injection of dependency IWarrior into parameter warrior of constructor of type AmbiguiousAttack
  1) Request for AmbiguiousAttack

Suggestions:
  1) Ensure that you have defined a binding for IWarrior only once.
at Ninject.KernelBase.Resolve(IRequest request) in KernelBase.cs: line 367
at Ninject.Planning.Targets.Target`1.GetValue(Type service, IContext parent) in Target.cs: line 197
at Ninject.Planning.Targets.Target`1.ResolveWithin(IContext parent) in Target.cs: line 165
at Ninject.Activation.Providers.StandardProvider.GetValue(IContext context, ITarget target) in StandardProvider.cs: line 97
at Ninject.Activation.Providers.StandardProvider.<>c__DisplayClass2.<Create>b__1(ITarget target) in StandardProvider.cs: line 81
at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext()
at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
at System.Linq.Enumerable.ToArray(IEnumerable`1 source)
at Ninject.Activation.Providers.StandardProvider.Create(IContext context) in StandardProvider.cs: line 81
at Ninject.Activation.Context.Resolve() in Context.cs: line 157
at Ninject.KernelBase.<>c__DisplayClass8.<Resolve>b__6(IBinding binding) in KernelBase.cs: line 367
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at System.Linq.Enumerable.<CastIterator>d__b1`1.MoveNext()
at System.Linq.Enumerable.Single(IEnumerable`1 source)
at Ninject.ResolutionExtensions.Get(IResolutionRoot root, IParameter[] parameters) in ResolutionExtensions.cs: line 37
at NinjectExamples.Chapter_9_ConstraintAttribute_Bindings.IfNoAttributeProvidedWillResolveToFirstBinding() in Foo.cs: line 30