@Override public boolean mutate(TestCase test,TestFactory factory){
  if (Randomness.nextDouble() >= Properties.P_CHANGE_PARAMETER)   return false;
  if (!isStatic()) {
    VariableReference source=getSource();
    List<VariableReference> objects=test.getObjects(source.getType(),getPosition());
    objects.remove(source);
    if (!objects.isEmpty()) {
      setSource(Randomness.choice(objects));
      return true;
    }
  }
  return false;
}

@ Override public boolean mutate ( TestCase test , TestFactory factory ) { if ( Randomness . nextDouble ( ) >= Properties . P_CHANGE_PARAMETER ) return false ; if ( ! isStatic ( ) ) { VariableReference source = getSource ( ) ; List < VariableReference > objects = test . getObjects ( source . getType ( ) , getPosition ( ) ) ; objects . remove ( source ) ; if ( ! objects . isEmpty ( ) ) { setSource ( Randomness . choice ( objects ) ) ; return true ; } } return false ; }
try to replace source of field with all possible choices
