KeyedServices.cs

namespace Examples
{
    using System.Reflection;
    using FluentAssertions;
    using NSubstitute;
    using Xunit;

    public interface IDuplicateService
    {
        int GetValue();
    }

    public class KeyedServices
    {
        private readonly IDuplicateService _firstService;
        private readonly IDuplicateService _secondService;

        public KeyedServices(IDuplicateService firstService, IDuplicateService secondService)
        {
            _firstService = firstService;
            _secondService = secondService;
        }

        public int AddValues()
        {
            var firstValue = _firstService.GetValue();
            var secondValue = _secondService.GetValue();

            return firstValue + secondValue;
        }
    }

    public class KeyedServicesTests : Tests<KeyedServices>
    {
        [Fact]
        public void CanConfigureKeyedServices()
        {
            Service<IDuplicateService>("A").GetValue().Returns(3);
            Service<IDuplicateService>("B").GetValue().Returns(15);

            var actual = SUT.AddValues();

            actual.Should().Be(18);
        }

        protected override object ResolveService(ParameterInfo parameter)
        {
            if (parameter.ParameterType != typeof(IDuplicateService))
            {
                return base.ResolveService(parameter);
            }

            if (parameter.Name == "firstService")
            {
                return ResolveService(parameter.ParameterType, "A");
            }

            return ResolveService(parameter.ParameterType, "B");
        }
    }
}