IOWA CITY — An Iowa City Veterans Affairs employee will testify before Congress on Tuesday about retaliation he says he faced after reporting veterans’ diagnostic exams had been canceled without doctors’ orders. Jeff Dettbarn, a former X-ray technologist, is one of three witnesses scheduled to testify about whistleblower concerns at a two-hour hearing before the House VA Committee’s subcommittee on oversight and investigations, he said Monday after flying into Washington, D.C.