sub stop_app {
    my ($self, $app) = @_;

    if(defined($app->{handle}) && $app->{handle}) {
        print "Killing app " . $app->{description} . "...\n";
        my $app_pid = $app->{handle}->GetProcessID();
        $app->{handle}->Kill(0);
        $app->{handle}->Wait(2000);
        $app->{handle} = undef;
        print "...killed.\n";
    } else {
        print "App " . $app->{description} . " already killed\n";
    }

}