Duplicated test scenario I would like to test

WpfViewModelFirst.Tests/MainWindowViewModelTests.cs

@@ -0,0 +1,34 @@
+using Moq;
+using WpfViewModelFirst.Part1;
+using WpfViewModelFirst.Part2;
+
+namespace WpfViewModelFirst.Tests
+{
+    public class MainWindowViewModelTests
+    {
+        [Fact]
+        public void Part1WillSetPart1ViewModelToCurrentViewModel()
+        {
+            Part1ViewModel part1ViewModel = new(() => _ = true);
+            Mock<IViewModelFactory> mockViewModelFactory = new Mock<IViewModelFactory>();
+            mockViewModelFactory.Setup(vmf => vmf.GetPart1ViewModel(It.IsAny<Action>()))
+                .Returns(part1ViewModel);
+            MainWindowViewModel main = new(mockViewModelFactory.Object);
+            main.Part1(null);
+            Assert.Equal(part1ViewModel, main.CurrentViewModel);
+        }
+        [Fact]
+        public void Part1CallbackIsSuccessfull()
+        {
+            Mock<IViewModelFactory> mockViewModelFactory = new Mock<IViewModelFactory>();
+            mockViewModelFactory.Setup(vmf => vmf.GetPart1ViewModel(It.IsAny<Action>()))
+                .Returns(() => new Part1ViewModel(() => Task.Delay(0)))
+                .Callback<Action>(c => c.Invoke());
+            mockViewModelFactory.Setup(vmf => vmf.GetPart2ViewModel())
+                .Returns(() => new Part2ViewModel());
+            MainWindowViewModel main = new(mockViewModelFactory.Object);
+            main.Part1(null);
+            Assert.IsType<Part2ViewModel>(main.CurrentViewModel);
+        }
+    }
+}

WpfViewModelFirst.Tests/Part1/Part1ViewModelTests.cs

@@ -0,0 +1,13 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace WpfViewModelFirst.Tests.Part1
+{
+    public class Part1ViewModelTests
+    {
+
+    }
+}

WpfViewModelFirst.Tests/Part2/Part2ViewModelTests.cs

@@ -0,0 +1,13 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace WpfViewModelFirst.Tests.Part2
+{
+    public class Part2ViewModelTests
+    {
+
+    }
+}

WpfViewModelFirst.Tests/Usings.cs

@@ -0,0 +1 @@
+global using Xunit;

WpfViewModelFirst.Tests/WpfViewModelFirst.Tests.csproj

@@ -0,0 +1,29 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net6.0-windows</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.0" />
+    <PackageReference Include="Moq" Version="4.18.2" />
+    <PackageReference Include="xunit" Version="2.4.2" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+    <PackageReference Include="coverlet.collector" Version="3.1.2">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\WpfViewModelFirst\WpfViewModelFirst.csproj" />
+  </ItemGroup>
+
+</Project>

WpfViewModelFirst.sln

@@ -3,13 +3,15 @@ Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio Version 17
 VisualStudioVersion = 17.3.32804.467
 MinimumVisualStudioVersion = 10.0.40219.1
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "WpfViewModelFirst", "WpfViewModelFirst\WpfViewModelFirst.csproj", "{E5611330-98DE-4571-A035-65576B2F8D4B}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "WpfViewModelFirst", "WpfViewModelFirst\WpfViewModelFirst.csproj", "{E5611330-98DE-4571-A035-65576B2F8D4B}"
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{90D6F27D-C403-4DF2-A570-D0DEECAC4062}"
 	ProjectSection(SolutionItems) = preProject
 		README.md = README.md
 	EndProjectSection
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "WpfViewModelFirst.Tests", "WpfViewModelFirst.Tests\WpfViewModelFirst.Tests.csproj", "{89753E08-BE0A-4FEA-B457-5486BB46EFEE}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -20,6 +22,10 @@ Global
 		{E5611330-98DE-4571-A035-65576B2F8D4B}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{E5611330-98DE-4571-A035-65576B2F8D4B}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{E5611330-98DE-4571-A035-65576B2F8D4B}.Release|Any CPU.Build.0 = Release|Any CPU
+		{89753E08-BE0A-4FEA-B457-5486BB46EFEE}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{89753E08-BE0A-4FEA-B457-5486BB46EFEE}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{89753E08-BE0A-4FEA-B457-5486BB46EFEE}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{89753E08-BE0A-4FEA-B457-5486BB46EFEE}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

WpfViewModelFirst/App.xaml.cs

@@ -18,7 +18,7 @@ namespace WpfViewModelFirst
             base.OnStartup(e);
             MainWindow mainWindow = new()
             {
-                DataContext = new MainWindowViewModel()
+                DataContext = new MainWindowViewModel(new ViewModelFactory())
             };
             mainWindow.Show();
         }

WpfViewModelFirst/IViewModelFactory.cs

@@ -0,0 +1,12 @@
+using System;
+using WpfViewModelFirst.Part1;
+using WpfViewModelFirst.Part2;
+
+namespace WpfViewModelFirst
+{
+    public interface IViewModelFactory
+    {
+        Part1ViewModel GetPart1ViewModel(Action finishAction);
+        Part2ViewModel GetPart2ViewModel();
+    }
+}

WpfViewModelFirst/MainWindowViewModel.cs

@@ -12,17 +12,20 @@ namespace WpfViewModelFirst
 {
     public class MainWindowViewModel : ViewModelBase
     {
-        public MainWindowViewModel()
+        public MainWindowViewModel(IViewModelFactory viewModelFactory)
         {
+            _viewModelFactory = viewModelFactory;
             StartCommand = new CustomCommand(Part1);
         }
+
+        private IViewModelFactory _viewModelFactory;
+
         public ICommand StartCommand { get; set; }
 
         public void Part1(object? e)
         {
             CurrentViewModel = null;
-            CurrentViewModel = new Part1ViewModel(Part1Action);
+            CurrentViewModel = _viewModelFactory.GetPart1ViewModel(Part1Action);
-//            MainFrameViewModel = new Part2ViewModel();
         }
         private void Part1Action()
         {
@@ -30,7 +33,7 @@ namespace WpfViewModelFirst
             Task delay = Task.Run(LongDelay).ContinueWith(c =>
             {
                 System.Diagnostics.Debug.WriteLine(c.Result);
-                CurrentViewModel = new Part2ViewModel();
+                CurrentViewModel = _viewModelFactory.GetPart2ViewModel();
             }, TaskContinuationOptions.OnlyOnRanToCompletion);
             //Task.Run(async () => await LongDelay()).ContinueWith(c =>
             //    {

WpfViewModelFirst/ViewModelFactory.cs

@@ -0,0 +1,20 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace WpfViewModelFirst
+{
+    public class ViewModelFactory : IViewModelFactory
+    {
+        public Part1.Part1ViewModel GetPart1ViewModel(Action finishAction)
+        {
+            return new(finishAction);
+        }
+        public Part2.Part2ViewModel GetPart2ViewModel()
+        {
+            return new();
+        }
+    }
+}