A simple form for testing form caching.
function form_test_cache_form($form, &$form_state) {
$form['title'] = array(
'#type' => 'textfield',
'#title' => 'Title',
'#required' => TRUE,
);
$form['submit'] = array(
'#type' => 'submit',
'#value' => 'Save',
);
return $form;
}