Raymond, the local pressure test is 15 lbs and must be maintained only 15 minutes. These tests vary from 10 pounds depending on jurisdiction. Becuse modifications to gas lines often require permits and testing, anyone doing this is advised to contact their local building department. Even where pressure testing is not required, a test using soapy water can reveal most significant leaks and should be done as a minimum verification.
The prof and Jason are both right in recommending extreme caution when working with gas. Although the origianl question was whether a gas line could be cut safely, the bonding of the additional fittings requires testing.