SingleParameter.cs

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

    public interface IDoSomething
    {
        string DoSomething(Guid id);
    }

    public class SingleParameter
    {
        private readonly IDoSomething _something;

        public SingleParameter(IDoSomething something)
        {
            _something = something;
        }

        public string Run(Guid id)
        {
            return _something.DoSomething(id);
        }
    }

    public class SingleParameterTests : Tests<SingleParameter>
    {
        [Fact]
        public void Test1()
        {
            var id = Guid.NewGuid();
            var expected = Guid.NewGuid().ToString();

            Service<IDoSomething>().DoSomething(id).Returns(expected);

            var actual = SUT.Run(id);

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