public function testEventCallbacks()
{
$et = new ET();
$et->c = 0;
$inc_c = function () use($et) {
$et->c++;
};
$checker = function ($event) {
return $event->name === 'ok';
};
// test checker
$et->on($checker, $inc_c);
$et->emit('ok');
$et->emit('nope');
$this->assertSame($et->c, 1);
// test removal
$et->removeListener($checker, $inc_c);
$et->emit('ok');
$this->assertSame($et->c, 1);
// test removeAllListeners
$et->on($checker, $inc_c);
$et->emit('ok');
$this->assertSame($et->c, 2);
$et->removeAllListeners($checker);
$et->emit('ok');
$this->assertSame($et->c, 2);
}