Reuters: BP Plc said it will begin pressure tests at its undersea oil leak in the Gulf of Mexico by midday on Tuesday after it placed a new containment cap and seal on the wellhead late on Monday. Kent Wells, senior vice president of exploration and production, told reporters that BP and government scientists would monitor the six- to 48-hour well integrity test at “very minute intervals.” If the test progresses as hoped, BP said no oil will flow from the well for the first time since a …