Add unit test.
Add unit test.

AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,SuperJMN/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,SuperJMN/Avalonia,AvaloniaUI/Avalonia,grokys/Perspex,SuperJMN/Avalonia,grokys/Perspex,SuperJMN/Avalonia,AvaloniaUI/Avalonia,SuperJMN/Avalonia,SuperJMN/Avalonia,SuperJMN/Avalonia,AvaloniaUI/Avalonia