EmuSen.LunaP.Testing 0.4.0

EmuSen.LunaP.Testing

The headless test harness LunaP tests itself with. Render capture, layout assertions and visual-tree queries for Avalonia windows, with no display and no GPU.

It is a separate package on purpose: EmuSen.LunaP references Avalonia and nothing else, and a harness needs xunit and Avalonia.Headless. Reference this from your test project only, and nothing your application ships gains a dependency.

dotnet add package EmuSen.LunaP.Testing

Using it

[assembly: AvaloniaTestApplication(typeof(TestAppBuilder))]
[assembly: CollectionBehavior(DisableTestParallelization = true)]

public class TestAppBuilder
{
    public static AppBuilder BuildAvaloniaApp() => LunaHeadless.BuildApp();
}

[Fact]
public Task The_settings_window_lays_out() => UiTest.Run(() =>
{
    var window = new SettingsWindow();
    window.Show();
    UiTest.AssertLaidOut(window, "settings");
});

LunaHeadless.BuildApp() builds the application with a real Skia render pass and LunaP's theme already included. That include is not cosmetic: without the real theme, templated controls have no template, render as nothing, and every assertion over them silently passes.

What it gives you

• UiTest.Run(body) — dispatches onto the one headless UI thread the session owns. Window and control construction is only valid there.
• UiTest.AssertLaidOut(window, name) — the assertion that earns its keep. A window that failed to lay out, or whose controls have no template, renders as one flat colour; counting distinct colours catches that where walking the logical tree does not.
• UiTest.AssertStable(name, build) — renders twice and asserts the two are identical. A window showing a clock, a pid or a frame counter fails by design, which is what makes it a usable baseline target.
• UiTest.Capture(window) → RGBA bytes, with Hash and DistinctColours.
• VisualQuery — FindPart<T>(), FindParts<T>(), CountParts<T>(), FindNamed<T>(name). For windows built in code there is no XAML namescope for GetControl to search, so these go through the visual tree.

Set EMUSEN_UI_DUMP to a directory to get a PNG of every capture in the run. Pixel-exact baselines are opt-in behind EMUSEN_UI_BASELINE, because they are an artefact of one machine's font rendering.

Test parallelisation must be off

[assembly: CollectionBehavior(DisableTestParallelization = true)] is required, and the harness refuses to start without it rather than letting you find out later.

Every test shares one headless application, and several things around it are process-global — the settings store, the diagnostics hook, and the applied theme's resource dictionary. xunit parallelises across test classes, so one class's constructor can replace another class's state mid-assertion. It presents as a suite that is green on your machine and red on CI, which is exactly how it was found.

If your suite serialises another way — a single shared collection — say so explicitly with UiSession.ParallelismIsHandled = true.

Licence

GPL-3.0-or-later.