WORCESTER — The architect that developer James E. Levin hired for the rehabilitation project at 5 May St. testified in federal court Monday that he never signed off on any reimbursement forms on Levin’s behalf out of concerns for the integrity of the process. Steven Petitpas, a longtime Boston architect, testified that he refused to sign the first reimbursement form he was forwarded after noticing an inaccurate statement, and was never again asked to approve any similar forms. “You can’t certify (work) that hasn’t been done, because you shouldn’t get paid for it,” Petitpas told jurors. The architect’s testimony was offered in support of the government’s contention that Levin, with help from the city’s former top housing official, Jacklyn M. Sutcivni, improperly received reimbursement of about $2 million in federal rehabilitation funds for work he did not perform in 2010 and 2011.