Guardian: BP began a series of critical tests on a new cap placed over its leaking oil well in the Gulf of Mexico today, expressing hope that it may finally bring the disaster under control. But the company warned that the process was “not simple stuff.” Oil was still gushing from the well, as expected, as engineers prepared to gradually choke off the flow by closing three vents on a new device lowered on to the blown-out well on Monday. Once the vents are closed, pressure readings will …