public function testSaveAndUnload()
{
$a = ['user' => [1 => ['name' => 'John', 'surname' => 'Smith', 'gender' => 'M'], 2 => ['name' => 'Sarah', 'surname' => 'Jones', 'gender' => 'F']]];
$p = new Persistence_Array($a);
$m = new Model_Male($p, 'user');
$m->load(1);
$this->assertTrue($m->loaded());
$m['gender'] = 'F';
$m->saveAndUnload();
$this->assertFalse($m->loaded());
$m = new Model_Female($p, 'user');
$m->load(1);
$this->assertTrue($m->loaded());
$this->assertEquals(['user' => [1 => ['name' => 'John', 'surname' => 'Smith', 'gender' => 'F'], 2 => ['name' => 'Sarah', 'surname' => 'Jones', 'gender' => 'F']]], $a);
}