Not really following how the functions relate to each other and where (so what variables are available, how), but you might try something like:
add_action('before_test_action', array($this, 'widget_test_func'));
public function widget_test_func( $instance) {
$boolean = (isset($instance['boolean'])) ? $instance['boolean'] : '';
if ($boolean == 'on') {
echo 'within widget test func';
}
}