WpfViewModelFirst/WpfViewModelFirst.Tests/MainWindowViewModelTests.cs

using Moq;
using WpfViewModelFirst.Part1;
using WpfViewModelFirst.Part2;

namespace WpfViewModelFirst.Tests
{
    public class MainWindowViewModelTests
    {
        [Fact]
        public void Part1WillSetPart1ViewModelToCurrentViewModel()
        {
            Part1ViewModel part1ViewModel = new(() => Task.CompletedTask);
            Mock<IViewModelFactory> mockViewModelFactory = new Mock<IViewModelFactory>();
            mockViewModelFactory.Setup(vmf => vmf.GetPart1ViewModel(It.IsAny<Func<Task>>()))
                .Returns(part1ViewModel);
            MainWindowViewModel main = new(mockViewModelFactory.Object);
            main.Part1(null);
            Assert.Equal(part1ViewModel, main.CurrentViewModel);
        }
        [Fact]
        public async Task Part1CallbackIsSuccessfull()
        {
            TaskCompletionSource<bool> taskCompletionSource = new TaskCompletionSource<bool>();
            Mock<IViewModelFactory> mockViewModelFactory = new Mock<IViewModelFactory>();
            mockViewModelFactory.Setup(vmf => vmf.GetPart1ViewModel(It.IsAny<Func<Task>>()))

                .Returns(() => new Part1ViewModel(() =>
                {
                    taskCompletionSource.SetResult(true);
                    return Task.CompletedTask;
                }))
                .Callback<Func<Task>>(c =>
                {
                    c.Invoke().ContinueWith(t =>
                    {
                        taskCompletionSource.SetResult(true);
                    });
                })
                ;
            mockViewModelFactory.Setup(vmf => vmf.GetPart2ViewModel())
                .Returns(() => new Part2ViewModel());
            MainWindowViewModel main = new(mockViewModelFactory.Object);
            main.Part1(null);
            await taskCompletionSource.Task.WaitAsync(CancellationToken.None);
            Assert.IsType<Part2ViewModel>(main.CurrentViewModel);
        }

        Func<Task> Part1Func()
        {
            return () => Task.CompletedTask;
        }
    }
}