如何在 .NET Core 中使用 xUnit 测试 Xamarin ViewModel？

Question

I want to test a Xamarin view model with xUnit. When the code is build using command line on Mac, the following error are show:

/usr/local/share/dotnet/sdk/3.1.300/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.FrameworkReferenceResolution.targets(283,5): error NETSDK1073: The FrameworkReference 'Microsoft.WindowsDesktop.App.WPF' was not recognized

If <GenerateErrorForMissingTargetingPacks>false</GenerateErrorForMissingTargetingPacks> is used on.csproj, the project compiles, but the following error are reported when I try to run the test.

System.BadImageFormatException: Duplicate type with name 'App.<>PropertyChangedEventArgs'

The view model are show below (part of the class). Fody and PropertyChanged.Fody are used to automate the implementation of INotifyPropertyChanged.

[AddINotifyPropertyChangedInterface]
public class ListaTarefasViewModel : ViewModelBase, IHandleViewAppearing, IHandleViewDisappearing
{

    public ListaTarefasViewModel(
        ITarefaService tarefaService,
        ITarefaRepository tarefaRepository,
        ITarefaRetornoItensRepository tarefaRetornoItensRepository,
        INotificationService notificationService,
        IUsuarioRepository usuarioRepository,
        IProdutoRepository produtoRepository)
    {
        this.tarefaService = tarefaService;
        this.tarefaRepository = tarefaRepository;
        this.notificationService = notificationService;
        this.usuarioRepository = usuarioRepository;
        this.tarefaRetornoItensRepository = tarefaRetornoItensRepository;
        this.produtoRepository = produtoRepository;
    }

    // ...
}

The test class:

public class ListaTarefasViewModelTest : IDisposable
{
    private readonly Mock<ListaTarefasViewModel> listaTarefasViewModelMock;

    public ListaTarefasViewModelTest()
    {
        listaTarefasViewModelMock = new Mock<ListaTarefasViewModel>();
    }

    public void Dispose()
    {
    }

    [Fact]
    public async Task ShouldConfigureTipoTarefaWhenInitializeAsync()
    {
        object tipoTarefa = TipoTarefaEnum.Inventario;
        await listaTarefasViewModelMock.Object.InitializeAsync(tipoTarefa);
        Assert.Equal(TipoTarefaEnum.Inventario, listaTarefasViewModelMock.Object.TipoTarefa);
    }
}

Answer 1

Build and Execution Errors

The error

/usr/local/share/dotnet/sdk/3.1.300/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.FrameworkReferenceResolution.targets(283,5): error NETSDK1073: The FrameworkReference 'Microsoft.WindowsDesktop.App.WPF' was not recognized

was caused by the use of the package Rg.Plugins.Popup , because it depends of WPF through Xamarin.Forms ( Xamarin.Forms.Platform.WPF ). This can be resolved by using <PrivateAssets>all</PrivateAssets> on the .csproj file.
Example:

<PackageReference Include="Rg.Plugins.Popup" Version="2.0.0.3">
    <PrivateAssets>all</PrivateAssets>
</PackageReference>

Reference about the .csproj file configuration: Package references (PackageReference) in project files

The error

System.BadImageFormatException: Duplicate type with name 'App.<>PropertyChangedEventArgs'

was solved by cleaning the entire solution or the shared project, but this is needed to be made before any test. This appears to be caused by Fody or PropertyChanged.Fody .
That are issues related to the this error, but none was resolved by now: issue on PropertyChanged.Fody repository and issue on MarcStan / resource-embedder repository .

Unit Test

Finally, the code uses Autofac and the test was made with xUnit . The class was tested with the mock getting all the dependencies from another mocks.

var tarefaService = Mock.Of<ITarefaService>();
var tarefaRepository = Mock.Of<ITarefaRepository>();
// ...
var mockListaTarefasViewModel = new Mock<ListaTarefasViewModel>(
    MockBehavior.Loose,
    tarefaService,
    tarefaRepository,
    // ..
);
mockListaTarefasViewModel
    .Setup(/* .. */)
    .Verifiable();
mockListaTarefasViewModel.Verify();