Replaces the brittle root.GetVisualDescendants().OfType<T>().Single() / .First()
pattern with a new WaitForComponent<T>() extension that polls until the requested
control is in the visual tree, then returns it. Avalonia.Headless tests routinely
queried the visual tree before lazily-templated panes (DataGrid, dock content)
had materialised, surfacing as intermittent 'Sequence contains no elements'
failures across the suite.
Assisted-by: Claude:claude-opus-4-7:Claude Code
Each tree-expansion, selection change, command execution, async wait and
key/mouse injection inside an [AvaloniaTest] now carries a short imperative
comment on the line above (e.g. "// expand typeNode", "// select methodA",
"// wait for assemblies to load", "// execute aboutCmd"). The comments are
the same scaffolding the manual debug-with-screenshot workflow uses to
follow what's happening at each breakpoint, surfaced into the committed
source so the tests are readable without the breakpoint markers attached.
Assisted-by: Claude:claude-opus-4-7:Claude Code
CommandLineArguments was already parsed at App.OnFrameworkInitializationCompleted
but never read. AssemblyTreeModel grows HandleCommandLineArgumentsAsync that
applies the parsed values:
Assisted-by: Claude:claude-opus-4-7:Claude Code
Siegfried Pammer