From Joomla! Documentation
The "API16" namespace is an archived namespace. This page contains information for a Joomla! version which is no longer supported. It exists only as a historical reference, it will not be improved and its content may be incomplete and/or contain broken links.
|test||Method to test if two values are equal. To use this rule, the form XML needs a validate attribute of equals and a field attribute that is equal to the field to test against.|
jimport( 'joomla.form.rules.equals' );