.NET MAUI Unit Testing with xUnit

Test Project Setup

Create a class library targeting the same TFM as your MAUI app:

<Project Sdk="Microsoft.NET.Sdk"> <PropertyGroup> <TargetFrameworks>net9.0;net10.0</TargetFrameworks> <IsPackable>false</IsPackable> <ImplicitUsings>enable</ImplicitUsings> <Nullable>enable</Nullable> </PropertyGroup>

<ItemGroup> <PackageReference Include="xunit" Version="2." /> <PackageReference Include="xunit.runner.visualstudio" Version="2." /> <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17." /> <PackageReference Include="coverlet.collector" Version="6." /> <PackageReference Include="Moq" Version="4.*" /> </ItemGroup>

<ItemGroup> <ProjectReference Include="..\MyApp\MyApp.csproj" /> </ItemGroup> </Project>

Use net9.0 or net10.0 (not a platform-specific TFM like net9.0-ios ) so xUnit can run on the desktop test host.

Conditional OutputType for App Projects

If your test project references an app project directly, prevent the app from building as an executable for the test TFM:

<!-- In the MAUI app .csproj --> <PropertyGroup Condition="'$(TargetFramework)' == 'net9.0'"> <OutputType>Library</OutputType> </PropertyGroup> <PropertyGroup Condition="'$(TargetFramework)' != 'net9.0'"> <OutputType>Exe</OutputType> </PropertyGroup>

xUnit Fundamentals

[Fact] — Single Test Case

public class CalculatorTests { [Fact] public void Add_TwoNumbers_ReturnsSum() { // Arrange var calculator = new Calculator();

    // Act
    var result = calculator.Add(2, 3);

    // Assert
    Assert.Equal(5, result);
}

}

[Theory] / [InlineData] — Parameterised Tests

public class ConverterTests { [Theory] [InlineData(0, 32)] [InlineData(100, 212)] [InlineData(-40, -40)] public void CelsiusToFahrenheit_ReturnsExpected(double celsius, double expected) { var result = TemperatureConverter.CelsiusToFahrenheit(celsius); Assert.Equal(expected, result, precision: 2); } }

Interface-First Architecture

Define service interfaces so ViewModels can be tested without MAUI platform dependencies:

public interface INavigationService { Task GoToAsync(string route); Task GoBackAsync(); }

public interface IDialogService { Task<bool> ConfirmAsync(string title, string message); }

Register implementations in MauiProgram.cs ; inject interfaces into ViewModels.

ViewModel Testing Pattern

public class ItemsViewModelTests { private readonly Mock<IItemService> _itemServiceMock = new(); private readonly Mock<INavigationService> _navMock = new();

private ItemsViewModel CreateSut() =>
    new(_itemServiceMock.Object, _navMock.Object);

[Fact]
public async Task LoadItems_PopulatesCollection()
{
    // Arrange
    var items = new List<Item> { new("A"), new("B") };
    _itemServiceMock.Setup(s => s.GetAllAsync()).ReturnsAsync(items);
    var sut = CreateSut();

    // Act
    await sut.LoadItemsCommand.ExecuteAsync(null);

    // Assert
    Assert.Equal(2, sut.Items.Count);
    Assert.False(sut.IsBusy);
}

[Fact]
public async Task SelectItem_NavigatesToDetail()
{
    // Arrange
    var sut = CreateSut();
    var item = new Item("Test");

    // Act
    await sut.SelectItemCommand.ExecuteAsync(item);

    // Assert
    _navMock.Verify(n => n.GoToAsync($"detail?id={item.Id}"), Times.Once);
}

}

Mocking Common MAUI Services

MAUI Service Mock Strategy

ISecureStorage

Mock<ISecureStorage> — stub GetAsync /SetAsync

IPreferences

Mock<IPreferences> — stub Get /Set /Remove

IConnectivity

Mock<IConnectivity> — return NetworkAccess

IGeolocation

Mock<IGeolocation> — return fixed Location

IFilePicker

Mock<IFilePicker> — return FileResult

IMediaPicker

Mock<IMediaPicker> — return FileResult

Shell navigation Abstract behind INavigationService

IDispatcher

Stub Dispatch to invoke action synchronously

Running Tests

Run all tests

dotnet test

Run with verbosity

dotnet test --verbosity normal

Filter by class or method

dotnet test --filter "FullyQualifiedName~ItemsViewModelTests"

Code coverage with coverlet (outputs to TestResults/)

dotnet test --collect:"XPlat Code Coverage"

Generate HTML coverage report (requires reportgenerator tool)

dotnet tool install -g dotnet-reportgenerator-globaltool reportgenerator -reports:TestResults/**/coverage.cobertura.xml
-targetdir:TestResults/CoverageReport -reporttypes:Html

On-Device Testing

For tests requiring real platform APIs (sensors, camera, Bluetooth), use the xunit.runner.devices package to run xUnit tests inside a MAUI app on a simulator or physical device. This is separate from dotnet test and runs within the app process.

Tips

• Keep ViewModels free of Application.Current , Shell.Current — wrap in injectable services.

• Use ObservableCollection<T> and [ObservableProperty] (MVVM Toolkit) for testable state.

• Assert on ViewModel properties and CanExecute , not UI bindings.

• Use TaskCompletionSource to test async waiting flows.

• Run dotnet test in CI to catch regressions early.