Testing

Testing

The headless platform

HeadlessPlatform runs forms without a screen: layout, input, focus, styles, bindings and the dispatcher all work as in a window, so a form is tested as a user would drive it.

[Fact]
public void TheGreetingNamesTheUser()
{
    var platform = new HeadlessPlatform();
    var form = new MainForm { Size = new Size(480, 320) };

    platform.CreateWindow(form);
    form.UpdateLayout();

    form.NameBox.Focus();
    HeadlessInput.TypeText(form, "Zeppelin");
    HeadlessInput.PressKey(form, Key.Enter);

    platform.PumpAll();                    // run what was queued to the dispatcher

    Assert.Equal("Hello, Zeppelin!", form.Greeting.Text);
}

Member
platform.CreateWindow(form)	Opens the form in a window of the given size
form.UpdateLayout()	Runs the pending layout now
platform.Pump(), PumpAll()	Runs one or all of the dispatcher's queued actions — BeginInvoke, timer ticks, changes of a data source from another thread
HeadlessInput.Click, DoubleClick, RightClick, MoveMouse	The mouse, at form coordinates
HeadlessInput.PressKey(form, key, modifiers)	A whole chord: pressed and released, the modifiers let go too
HeadlessInput.TypeText, Compose, CommitComposition	Typing and input-method composition
HeadlessInput.Tap, Swipe, TouchDown/Move/Up	Touch, with flings

Element positions for the mouse come from the layout: element.GetAbsolutePosition() and element.ActualSize.

The headless window records what the form asked of it — HeadlessWindow.IsTopMost, MinimumSizeLimit, MaximumSizeLimit, CenterOnScreenCount — so window behaviour is tested too.

Tests that open headless windows share the process-wide state of the UI thread and the keyboard: run them in one xUnit collection, not in parallel.

Drawing

ElementTreeRenderer.Draw(element, graphics) draws a tree into any Graphics. A HeadlessGraphics subclass that records the calls checks what was drawn without pixels:

private sealed class FillRecorder : HeadlessGraphics
{
    public List<Color> Fills { get; } = [];

    public override void FillRectangle(Rectangle rect, Color color) => Fills.Add(color);
}

element.RenderToImage() renders the element into an image where a renderer is registered.

Snapshots

The framework's own visual tests compare renders with reference images in tests/ZeppelinForms.UnitTests/Snapshots/Expected/{win,linux} — text rendering differs between the platforms, so each has its set.

• bash: ZF_UPDATE_SNAPSHOTS=true dotnet test
• PowerShell: $env:ZF_UPDATE_SNAPSHOTS='true'; dotnet test

ZF_CREATE_SNAPSHOTS=true only adds the missing ones.

Benchmarks

bench/ZeppelinForms.Benchmarks measures layout, rendering, text and the scrolling of a virtualized list against a stored baseline:

dotnet run --project bench/ZeppelinForms.Benchmarks -c Release
dotnet run --project bench/ZeppelinForms.Benchmarks -c Release -- --update-baseline

Run-to-run spread on a desktop reaches tens of percent: take the median of three, and record a baseline only on a quiet machine.