Construct testable business layer logic

Question

I am building an applications in .net/c#/Entity Framework that uses a layered architecture. The applications interface to the outside world is a WCF service Layer. Underneat

Answer 1

I generally use IServices, Services, and MockServices.

• IServices provides the available operations that all business logic must invoke methods on.
• Services is the data access layer that my code-behind injects into view-model (i.e. actual database).
• MockServices is the data access layer that my unit tests injects to the view-model (i.e. mock data).

IServices:

public interface IServices
{
    IEnumerable<Warehouse> LoadSupply(Lookup lookup);
    IEnumerable<Demand> LoadDemand(IEnumerable<string> stockCodes, int daysFilter, Lookup lookup);

    IEnumerable<Inventory> LoadParts(int daysFilter);
    Narration LoadNarration(string stockCode);
    IEnumerable<PurchaseHistory> LoadPurchaseHistory(string stockCode);

    IEnumerable<StockAlternative> LoadAlternativeStockCodes();
    AdditionalInfo GetSupplier(string stockCode);
}

MockServices:

public class MockServices : IServices
{
    #region Constants
    const int DEFAULT_TIMELINE = 30;
    #endregion

    #region Singleton
    static MockServices _mockServices = null;

    private MockServices()
    {
    }

    public static MockServices Instance
    {
        get
        {
            if (_mockServices == null)
            {
                _mockServices = new MockServices();
            }

            return _mockServices;
        }
    }
    #endregion

    #region Members
    IEnumerable<Warehouse> _supply = null;
    IEnumerable<Demand> _demand = null;
    IEnumerable<StockAlternative> _stockAlternatives = null;
    IConfirmationInteraction _refreshConfirmationDialog = null;
    IConfirmationInteraction _extendedTimelineConfirmationDialog = null;
    #endregion

    #region Boot
    public MockServices(IEnumerable<Warehouse> supply, IEnumerable<Demand> demand, IEnumerable<StockAlternative> stockAlternatives, IConfirmationInteraction refreshConfirmationDialog, IConfirmationInteraction extendedTimelineConfirmationDialog)
    {
        _supply = supply;
        _demand = demand;
        _stockAlternatives = stockAlternatives;
        _refreshConfirmationDialog = refreshConfirmationDialog;
        _extendedTimelineConfirmationDialog = extendedTimelineConfirmationDialog;
    }

    public IEnumerable<StockAlternative> LoadAlternativeStockCodes()
    {
        return _stockAlternatives;
    }

    public IEnumerable<Warehouse> LoadSupply(Lookup lookup)
    {
        return _supply;
    }

    public IEnumerable<Demand> LoadDemand(IEnumerable<string> stockCodes, int daysFilter, Syspro.Business.Lookup lookup)
    {
        return _demand;
    }

    public IEnumerable<Inventory> LoadParts(int daysFilter)
    {
        var job1 = new Job() { Id = Globals.jobId1, AssembledRequiredDate = DateTime.Now, StockCode = Globals.stockCode100 };
        var job2 = new Job() { Id = Globals.jobId2, AssembledRequiredDate = DateTime.Now, StockCode = Globals.stockCode200 };
        var job3 = new Job() { Id = Globals.jobId3, AssembledRequiredDate = DateTime.Now, StockCode = Globals.stockCode300 };

        return new HashSet<Inventory>()
        {
            new Inventory() { StockCode = Globals.stockCode100, UnitQTYRequired = 1, Category = "Category_1", Details = new PartDetails() { Warehouse = Globals.Instance.warehouse1, Job = job1} },
            new Inventory() { StockCode = Globals.stockCode200, UnitQTYRequired = 2, Category = "Category_1", Details = new PartDetails() { Warehouse = Globals.Instance.warehouse1, Job = job2} },
            new Inventory() { StockCode = Globals.stockCode300, UnitQTYRequired = 3, Category = "Category_1", Details = new PartDetails() { Warehouse = Globals.Instance.warehouse1, Job = job3} },
        };
    }
    #endregion

    #region Selection
    public Narration LoadNarration(string stockCode)
    {
        return new Narration()
        {
            Text = "Some description"
        };
    }

    public IEnumerable<PurchaseHistory> LoadPurchaseHistory(string stockCode)
    {
        return new List<PurchaseHistory>();
    }

    public AdditionalInfo GetSupplier(string stockCode)
    {
        return new AdditionalInfo()
        {
            SupplierName = "Some supplier name"
        };
    }
    #endregion

    #region Creation
    public Inject Dependencies(IEnumerable<Warehouse> supply, IEnumerable<Demand> demand, IEnumerable<StockAlternative> stockAlternatives, IConfirmationInteraction refreshConfirmation = null, IConfirmationInteraction extendedTimelineConfirmation = null)
    {
        return new Inject()
        {
            Services = new MockServices(supply, demand, stockAlternatives, refreshConfirmation, extendedTimelineConfirmation),

            Lookup = new Lookup()
            {
                PartKeyToCachedParts = new Dictionary<string, Inventory>(),
                PartkeyToStockcode = new Dictionary<string, string>(),
                DaysRemainingToCompletedJobs = new Dictionary<int, HashSet<Job>>(),
.
.
.

            },

            DaysFilterDefault = DEFAULT_TIMELINE,
            FilterOnShortage = true,
            PartCache = null
        };
    }

    public List<StockAlternative> Alternatives()
    {
        var stockAlternatives = new List<StockAlternative>() { new StockAlternative() { StockCode = Globals.stockCode100, AlternativeStockcode = Globals.stockCode100Alt1 } };
        return stockAlternatives;
    }

    public List<Demand> Demand()
    {
        var demand = new List<Demand>()
        {
            new Demand(){ Job = new Job{ Id = Globals.jobId1, StockCode = Globals.stockCode100, AssembledRequiredDate = DateTime.Now}, StockCode = Globals.stockCode100, RequiredQTY = 1}, 
            new Demand(){ Job = new Job{ Id = Globals.jobId2, StockCode = Globals.stockCode200, AssembledRequiredDate = DateTime.Now}, StockCode = Globals.stockCode200, RequiredQTY = 2}, 
        };
        return demand;
    }

    public List<Warehouse> Supply()
    {
        var supply = new List<Warehouse>() 
        { 
            Globals.Instance.warehouse1, 
            Globals.Instance.warehouse2, 
            Globals.Instance.warehouse3,
        };
        return supply;
    }
    #endregion
}

Services:

public class Services : IServices
{
    #region Singleton
    static Services services = null;

    private Services()
    {
    }

    public static Services Instance
    {
        get
        {
            if (services == null)
            {
                services = new Services();
            }

            return services;
        }
    }
    #endregion

    public IEnumerable<Inventory> LoadParts(int daysFilter)
    {
        return InventoryRepository.Instance.Get(daysFilter);
    }

    public IEnumerable<Warehouse> LoadSupply(Lookup lookup)
    {
        return SupplyRepository.Instance.Get(lookup);
    }

    public IEnumerable<StockAlternative> LoadAlternativeStockCodes()
    {
        return InventoryRepository.Instance.GetAlternatives();
    }

    public IEnumerable<Demand> LoadDemand(IEnumerable<string> stockCodes, int daysFilter, Lookup lookup)
    {
        return DemandRepository.Instance.Get(stockCodes, daysFilter, lookup);
    }
.
.
.

Unit Test:

    [TestMethod]
    public void shortage_exists()
    {
        // Setup
        var supply = new List<Warehouse>() { Globals.Instance.warehouse1, Globals.Instance.warehouse2, Globals.Instance.warehouse3 };
        Globals.Instance.warehouse1.TotalQty = 1;
        Globals.Instance.warehouse2.TotalQty = 2;
        Globals.Instance.warehouse3.TotalQty = 3;

        var demand = new List<Demand>()
        {
            new Demand(){ Job = new Job{ Id = Globals.jobId1, StockCode = Globals.stockCode100, AssembledRequiredDate = DateTime.Now}, StockCode = Globals.stockCode100, RequiredQTY = 1}, 
            new Demand(){ Job = new Job{ Id = Globals.jobId2, StockCode = Globals.stockCode200, AssembledRequiredDate = DateTime.Now}, StockCode = Globals.stockCode200, RequiredQTY = 3}, 
            new Demand(){ Job = new Job{ Id = Globals.jobId3, StockCode = Globals.stockCode300, AssembledRequiredDate = DateTime.Now}, StockCode = Globals.stockCode300, RequiredQTY = 4}, 
        };

        var alternatives = _mock.Alternatives();
        var dependencies = _mock.Dependencies(supply, demand, alternatives);

        var viewModel = new MainViewModel();
        viewModel.Register(dependencies);

        // Test
        viewModel.Load();

        AwaitCompletion(viewModel);

        // Verify
        var part100IsNotShort = dependencies.PartCache.Where(p => (p.StockCode == Globals.stockCode100) && (!p.HasShortage)).Single() != null;
        var part200IsShort = dependencies.PartCache.Where(p => (p.StockCode == Globals.stockCode200) && (p.HasShortage)).Single() != null;
        var part300IsShort = dependencies.PartCache.Where(p => (p.StockCode == Globals.stockCode300) && (p.HasShortage)).Single() != null;

        Assert.AreEqual(true, part100IsNotShort &&
                                part200IsShort &&
                                part300IsShort);
    }

CodeBehnd:

    public MainWindow()
    {
        InitializeComponent();

        this.Loaded += (s, e) =>
            {
                this.viewModel = this.DataContext as MainViewModel;

                var dependencies = GetDependencies();
                this.viewModel.Register(dependencies);
.
.
.

ViewModel:

    public MyViewModel()
    {
.
.
.
    public void Register(Inject dependencies)
    {
        try
        {
            this.Injected = dependencies;

            this.Injected.RefreshConfirmation.RequestConfirmation += (message, caption) =>
                {
                    var result = MessageBox.Show(message, caption, MessageBoxButton.YesNo, MessageBoxImage.Question);
                    return result;
                };

            this.Injected.ExtendTimelineConfirmation.RequestConfirmation += (message, caption) =>
                {
                    var result = MessageBox.Show(message, caption, MessageBoxButton.YesNo, MessageBoxImage.Question);
                    return result;
                };

.
.
.
        }

        catch (Exception ex)
        {
            Debug.WriteLine(ex.GetBaseException().Message);
        }
    }