function test_add_filter()
{
$context = new LiquidContext();
$context->add_filters(new HiFilter());
$this->assertEqual('hi? hi!', $context->invoke('hi', 'hi?'));
$context = new LiquidContext();
$this->assertEqual('hi?', $context->invoke('hi', 'hi?'));
$context->add_filters(new HiFilter());
$this->assertEqual('hi? hi!', $context->invoke('hi', 'hi?'));
}