NavPilot, LASORS is your friend - sections G and J. The ATPL theory passes are good for 36 months for you to get a CPL and IR - then good for obtaining an ATPL provided you meet the other requirements within 7 years of the most recent IR renewal.
There is an ATPL Skill Test, to be taken in an appropriate multi-pilot aircraft (or sim, presumably), which may be combined with the test for issuing or revalidating such a type rating. You can only take it after you meet the other requirements for ATPL issue (flying hours in particular).