function testRootFieldSet()
{
/* Given a nested set of FormField, CompositeField, and FieldSet objects */
$fieldSet = new FieldSet($root = new TabSet("Root", $main = new Tab("Main", $a = new TextField("A"), $b = new TextField("B"))));
/* rootFieldSet() should always evaluate to the same object: the topmost fieldset */
$this->assertSame($fieldSet, $fieldSet->rootFieldSet());
$this->assertSame($fieldSet, $root->rootFieldSet());
$this->assertSame($fieldSet, $main->rootFieldSet());
$this->assertSame($fieldSet, $a->rootFieldSet());
$this->assertSame($fieldSet, $b->rootFieldSet());
/* If we push additional fields, they should also have the same rootFieldSet() */
$root->push($other = new Tab("Other"));
$other->push($c = new TextField("C"));
$root->push($third = new Tab("Third", $d = new TextField("D")));
$this->assertSame($fieldSet, $other->rootFieldSet());
$this->assertSame($fieldSet, $third->rootFieldSet());
$this->assertSame($fieldSet, $c->rootFieldSet());
$this->assertSame($fieldSet, $d->rootFieldSet());
}
