The University of St Andrews in Scotland will on Saturday roll out free mass Covid tests for all students before they travel home for the Christmas holidays.The tests are voluntary, but students have been advised to take them to avoid spreading the virus to family or friends over the holidays. Students will be offered a lateral-flow test which involves taking a swab from the mouth and nose in a process that takes just minutes. Students will be notified of the test result by email or text within 24 hours. The UK's four constituent nations, England, Scotland, Wales and Northern Ireland, agreed earlier this week to ease rules over Christmas, allowing three households to mix over a period of five days.