.NET MAUI

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Advanced & Enterprise Advanced Data Binding & Collections App Lifecycle & Windows Best Practices & Architecture Concurrency & Threading Controls & Views Data Binding & MVVM Dependency Injection & Services Desktop - WinUI & Mac Catalyst Device Features & Essentials Fonts, Icons & Media Forms, Input & Validation Fundamentals & Architecture Gestures & Animations Graphics & Drawing Local Storage & Data Maps & Location Migration from Xamarin.Forms Native Interop & Libraries Networking & APIs

.NET MAUI

Testing & Debugging

Q: How do you unit test a MAUI app's logic?

Put testable logic in view models and services (plain .NET classes), then test them with xUnit/NUnit/MSTest in a separate class-library targeting a plain TFM (e.g., net8.0). Because MVVM keeps logic out of the UI, you can instantiate view models, inject fakes, and assert on properties and commands without a device.

Q: How do you mock platform/device services for testing?

Abstract device features behind interfaces (e.g., IGeolocation, IConnectivity—MAUI already provides interfaces for many Essentials APIs) and inject them. In tests supply fakes/mocks. Avoid calling static Essentials members directly in logic; depend on the interface so tests don't touch real hardware.

Q: How do you debug platform-specific issues in MAUI?

Select the target platform head in the debugger, use conditional breakpoints and the platform's native logs (logcat for Android, Console/Instruments for iOS). Reproduce on the specific platform, inspect the native view via handlers, and use #if-guarded logging. The Live Visual Tree helps inspect the UI hierarchy.

Q: What is Hot Reload and what are its limitations in MAUI?

XAML Hot Reload applies markup changes to a running app without rebuilding; .NET Hot Reload applies many C# edits live. They speed up UI iteration greatly. Limitations: some structural code changes, new fields, or signature changes require a full rebuild, and not every edit is supported—expect occasional restarts.

Q: How do you write UI/integration tests for MAUI apps?

Use Appium (cross-platform UI automation) or platform tools to drive the running app, asserting on visible elements via automation IDs. Set AutomationId on controls for stable selectors. For device-hosted unit tests, MAUI supports a device test runner. UI tests are slower and more brittle, so cover critical flows and keep most logic in fast unit tests.

Q: How do you capture and diagnose crashes in production MAUI apps?

Integrate a crash/telemetry SDK (App Center successor/Sentry/Application Insights) to capture unhandled exceptions with stack traces, device info, and breadcrumbs. Hook AppDomain.UnhandledException and per-platform handlers, symbolicate native crashes with debug symbols, and monitor crash-free rates per release.

6 question(s)

How do you unit test a MAUI app's logic?

Beginner

Put testable logic in view models and services (plain .NET classes), then test them with xUnit/NUnit/MSTest in a separate class-library targeting a plain TFM (e.g., net8.0). Because MVVM keeps logic out of the UI, you can instantiate view models, inject fakes, and assert on properties and commands without a device.

[Fact]
public async Task Login_SetsIsBusy_False_After_Complete()
{
    var vm = new LoginViewModel(new FakeAuth());
    await vm.LoginCommand.ExecuteAsync(null);
    Assert.False(vm.IsBusy);
}

Real-world example A team runs hundreds of view-model tests in CI in seconds, with no emulator required.

Common follow-ups: Why keep logic out of code-behind? | What TFM does the test project use?

MVVM Testing & Debugging Dependency Injection

How do you mock platform/device services for testing?

Intermediate

Abstract device features behind interfaces (e.g., IGeolocation, IConnectivity—MAUI already provides interfaces for many Essentials APIs) and inject them. In tests supply fakes/mocks. Avoid calling static Essentials members directly in logic; depend on the interface so tests don't touch real hardware.

// Production: inject IConnectivity; Test: pass a stub
public SyncViewModel(IConnectivity connectivity) => _c = connectivity;

var vm = new SyncViewModel(new StubConnectivity(NetworkAccess.None));

Real-world example A sync view model is tested for its offline path by injecting a stub connectivity that reports no network.

Common follow-ups: Do Essentials expose interfaces? | Why avoid static calls in logic?

Testing & Debugging Dependency Injection Device Features

How do you debug platform-specific issues in MAUI?

Intermediate

Select the target platform head in the debugger, use conditional breakpoints and the platform's native logs (logcat for Android, Console/Instruments for iOS). Reproduce on the specific platform, inspect the native view via handlers, and use #if-guarded logging. The Live Visual Tree helps inspect the UI hierarchy.

#if ANDROID
Android.Util.Log.Debug("MyApp", $"State: {state}");
#endif

Real-world example An Android-only layout glitch is diagnosed by logging to logcat and inspecting the native view tree, then fixed with a handler tweak.

Common follow-ups: Where do Android logs go? | How do you inspect the native view?

Debugging Platform Integration Handlers

What is Hot Reload and what are its limitations in MAUI?

Intermediate

XAML Hot Reload applies markup changes to a running app without rebuilding; .NET Hot Reload applies many C# edits live. They speed up UI iteration greatly. Limitations: some structural code changes, new fields, or signature changes require a full rebuild, and not every edit is supported—expect occasional restarts.

Real-world example A developer tweaks padding and colors in XAML and sees updates instantly on the device, iterating on layout in seconds.

Common follow-ups: What changes force a rebuild? | Does Hot Reload cover C#?

Debugging XAML & UI Layouts Productivity

How do you write UI/integration tests for MAUI apps?

Advanced

Use Appium (cross-platform UI automation) or platform tools to drive the running app, asserting on visible elements via automation IDs. Set AutomationId on controls for stable selectors. For device-hosted unit tests, MAUI supports a device test runner. UI tests are slower and more brittle, so cover critical flows and keep most logic in fast unit tests.

<Button Text="Login" AutomationId="LoginButton" />
// Appium: driver.FindElement(MobileBy.AccessibilityId("LoginButton")).Click();

Real-world example A smoke suite runs the login-to-dashboard flow on real devices nightly via Appium, catching integration regressions.

Common follow-ups: Why set AutomationId? | Why keep most tests at the unit level?

Testing & Debugging UI Testing MVVM

How do you capture and diagnose crashes in production MAUI apps?

Advanced

Integrate a crash/telemetry SDK (App Center successor/Sentry/Application Insights) to capture unhandled exceptions with stack traces, device info, and breadcrumbs. Hook AppDomain.UnhandledException and per-platform handlers, symbolicate native crashes with debug symbols, and monitor crash-free rates per release.

AppDomain.CurrentDomain.UnhandledException += (s, e) =>
    _telemetry.TrackException((Exception)e.ExceptionObject);

Real-world example A spike in crashes after a release is pinpointed to one device model via telemetry stack traces and hotfixed the same day.

Common follow-ups: How do you symbolicate native crashes? | What is a crash-free rate?

Debugging Deployment Monitoring