Builds a simple form to test form button classes.
function form_test_button_class($form, &$form_state) {
$form['button'] = array(
'#type' => 'button',
'#value' => 'test',
'#button_type' => 'foo',
);
$form['delete'] = array(
'#type' => 'button',
'#value' => 'Delete',
'#button_type' => 'danger',
);
return $form;
}