app_test.rb

framework 'cocoa'

class Application

  def applicationDidFinishLaunching(notification)
    frame = NSRect.new(NSPoint.new(100, 100), NSSize.new(300, 300))
    @main_window = NSWindow.alloc.initWithContentRect( 
      frame, 
      :styleMask => (NSTitledWindowMask | NSClosableWindowMask),
      :backing => NSBackingStoreBuffered,
      :defer => false
    )
  end

end

NSApplication.sharedApplication.delegate = Application.new
NSApplication.sharedApplication.run