AcceptanceTest.cs

using System;
using System.Threading.Tasks;
using FluentAssertions;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace CleanArchitecture.Requestor.Test
{
    [TestClass]
    public sealed class AcceptanceTest
    {
        private string addedUser = string.Empty;
        
        public AcceptanceTest()
        {
            RequestBuilder.Instance.Register("add_user", () => new AddUserRequestBuilder());
            UseCaseFactory.Instance.Register("add_user", () => new AddUserUseCase(n => this.addedUser = n));
        }
        
        [TestMethod]
        public void ExecuteUseCase()
        {
            var request = BuildRequest();
            
            ExecuteUseCase();
            
            this.addedUser.Should().Be("Stefan");
            

            IRequest BuildRequest()
            {
                return RequestBuilder.Instance.BuildRequest("add_user", new RequestProperties()
                    .Set("user_name", "Stefan"));
            }
            
            void ExecuteUseCase()
            {
                UseCaseFactory.Instance
                    .CreateUseCase("add_user")
                    .Execute(request);
            }
        }

        private sealed class AddUserRequestBuilder : IRequestBuilder
        {
            public IRequest BuildRequestFrom(RequestProperties properties)
            {
                return new AddUserRequest
                {
                    UserName = properties.GetString("user_name")
                };
            } 
        }

        private sealed class AddUserRequest : IRequest
        {
            public string UserName;
        }

        private sealed class AddUserUseCase : IUseCase
        {
            private readonly Action<string> onUserAdded;

            public AddUserUseCase(Action<string> onUserAdded)
            {
                this.onUserAdded = onUserAdded;
            }
            
            public Task Execute(IRequest request)
            {
                var r = (AddUserRequest)request;
                this.onUserAdded(r.UserName);
                
                return Task.CompletedTask;
            }
        }
    }
}