public void ApplyToTreLevelByLevel_TakesAnAction_AppliesItToAllNodes()
{
float count = 0;
TreeVisitor.ApplyToTreeLevelByLevel(_tree, node => count += node.Sum(n => n.Space.Width));
Assert.That(count, Is.EqualTo(31));
}
public void ApplyToTreeLevelByLevel_NullArgs_ThrowsError()
{
Assert.That(() => TreeVisitor.ApplyToTreeLevelByLevel(null !, tree => { }),
Throws.ArgumentNullException);
Assert.That(() => TreeVisitor.ApplyToTreeLevelByLevel(new Widget(RectangleF.Empty), null !),
Throws.ArgumentNullException);
}