public function test_clear_returns_an_empty_collection()
{
$col = new Collection('TestClassA', [new TestClassA(1)]);
//col will have one
$this->assertEquals(1, $col->count());
//empty should have no items
$empty = $col->clear();
$this->assertEquals(0, $empty->count());
//col should remain unchanged
$this->assertEquals(1, $col->count());
}