See Brian Ludmer's article on children being hurt in the divorce process
Central Ohio Parental Alienation believes that asking a child to testifying against a parent is essentially asking a child to betray a parent. That is a primal betrayal. Testifying against a parent further triangulates a child into the parental conflict. If there is abuse (other than the harmful psychological abuse of parental alienation), sure, then have the child testify in criminal court.