[TYPO3-english] xclass TestSetup class

[Tomasz Krawczyk]

Hi list,

I make changes to Imagickimg extension (graphics processing where exec() 
is disabled).
I'm trying to xclass TestSetup

	$GLOBALS['TYPO3_CONF_VARS']['SYS']['Objects']['TYPO3\\CMS\\Core\\Imaging\\GraphicalFunctions'] = array(
		'className' => 'ImagickImgTeam\\Imagickimg\\Xclass\\GraphicalFunctions'
	);
	$GLOBALS['TYPO3_CONF_VARS']['SYS']['Objects']['TYPO3\\CMS\\Frontend\\Imaging\\GifBuilder'] = array(
		'className' => 'ImagickImgTeam\\Imagickimg\\Xclass\\GifBuilder'
	);
	$GLOBALS['TYPO3_CONF_VARS']['SYS']['Objects']['TYPO3\\CMS\\Backend\\View\\ThumbnailView'] = array(
		'className' => 'ImagickImgTeam\\Imagickimg\\Xclass\\ThumbnailView'
	);
(...)
	$GLOBALS['TYPO3_CONF_VARS']['SYS']['Objects']['TYPO3\\CMS\\Install\\Controller\\Action\\Tool\\TestSetup'] = array(
		'className' => 'ImagickImgTeam\\Imagickimg\\Xclass\\TestSetup'
	);

But still TestSetup do not work while other classes are xclassed and 
work fine.
Is Install Tool writen in different way?
What should I do to xclass this class?

cheers
Tomek