public function testRemove()
{
$set1 = new Set();
$set2 = new Set([100, 200]);
$set1->add(200);
$set1->add(300);
$set2->retainAll($set1);
$this->assertEquals($set1->toArray(), [200, 300]);
$this->assertEquals($set2->toArray(), [200]);
$this->assertFalse($set1->equals($set2));
$this->assertFalse($set2->equals($set1));
$set1->remove(300);
$this->assertTrue($set1->equals($set2));
$this->assertTrue($set2->equals($set1));
$set1->removeAll($set2);
$this->assertTrue($set1->isEmpty());
$this->assertFalse($set2->isEmpty());
}