add_action not working within widget() of WP_Wdiget

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';

    }

}