test: add app-level smoke baselines and mobile CI test jobs

Co-authored-by: Velik <hongochai10@users.noreply.github.com>

apps/app-client-base-net/tests/AppClientBase.UnitTests/ViewModels/MainViewModelTests.cs

@@ -0,0 +1,81 @@
+using AppClientBase.Services;
+using AppClientBase.ViewModels;
+using FluentAssertions;
+using Xunit;
+
+namespace AppClientBase.UnitTests.ViewModels;
+
+/// <summary>
+/// EN: Unit tests for main view model behavior.
+/// VI: Unit tests cho hành vi của main view model.
+/// </summary>
+public class MainViewModelTests
+{
+    [Fact]
+    public void Constructor_ShouldSetDefaultTitleAndWelcomeMessage()
+    {
+        // Arrange
+        var navigationService = new FakeNavigationService();
+        var settingsService = new FakeSettingsService();
+
+        // Act
+        var viewModel = new MainViewModel(navigationService, settingsService);
+
+        // Assert
+        viewModel.Title.Should().Be("Home");
+        viewModel.WelcomeMessage.Should().Be("Welcome to AppClientBase!");
+        viewModel.ClickCount.Should().Be(0);
+        viewModel.ButtonText.Should().Be("Click me");
+    }
+
+    [Fact]
+    public void IncrementCounterCommand_ShouldIncreaseCountAndPersistSetting()
+    {
+        // Arrange
+        var navigationService = new FakeNavigationService();
+        var settingsService = new FakeSettingsService();
+        var viewModel = new MainViewModel(navigationService, settingsService);
+
+        // Act
+        viewModel.IncrementCounterCommand.Execute(null);
+        viewModel.IncrementCounterCommand.Execute(null);
+
+        // Assert
+        viewModel.ClickCount.Should().Be(2);
+        viewModel.ButtonText.Should().Be("Clicked 2 times");
+        settingsService.Get("ClickCount", 0).Should().Be(2);
+    }
+
+    private sealed class FakeNavigationService : INavigationService
+    {
+        public Task GoToAsync(string route, IDictionary<string, object>? parameters = null) => Task.CompletedTask;
+
+        public Task GoBackAsync() => Task.CompletedTask;
+    }
+
+    private sealed class FakeSettingsService : ISettingsService
+    {
+        private readonly Dictionary<string, object?> _store = new(StringComparer.Ordinal);
+
+        public T Get<T>(string key, T defaultValue)
+        {
+            if (_store.TryGetValue(key, out var value) && value is T typed)
+            {
+                return typed;
+            }
+
+            return defaultValue;
+        }
+
+        public void Set<T>(string key, T value)
+        {
+            _store[key] = value;
+        }
+
+        public bool Contains(string key) => _store.ContainsKey(key);
+
+        public void Remove(string key) => _store.Remove(key);
+
+        public void Clear() => _store.Clear();
+    }
+}