Now that a leak has been fixed, BP is ready to test the latest cap it’s put on the busted rig spewing oil into the Gulf. National Incident Commander Thad Allen said that BP would start testing Thursday and had already begun some preliminary steps, including reopening two valves that had been closed. The procedure can begin once the cap seals are tested again and underwater robots are moved into place. Work was delayed Wednesday when scientists discovered a leak in the seal between the cap and the choke line that vents some oil; the whole choke line assembly was switched out overnight. The cap is a stopgap until the relief well is drilled. It’s unclear whether the device will be used to channel oil to collection vessels on the surface or to shut off the oil entirely.