anchor.diff:          {merge, success, _L2, _L1} -> ok
       end,
       % no renews during merge!
  -    ?assert(0 =:= mockup_l_on_cseq:get_renewal_counter()),
  +    ?equals(mockup_l_on_cseq:get_renewal_counter(), 0),
       % check L1
  -    case l_on_cseq:read(l_on_cseq:get_id(L1)) of
  -        {ok, L1_} -> ?assert(L1_ =:= prbr_bottom);
  -        {fail, not_found} -> ?assert(false)
  -    end,
  +    ?equals(l_on_cseq:read(l_on_cseq:get_id(L1)), {ok, prbr_bottom}),
       % check L2
       case l_on_cseq:read(l_on_cseq:get_id(L2)) of
           {ok, L2_} ->
  -            ?assert(l_on_cseq:get_range(L2_) =:= intervals:union(l_on_cseq:get_range(L1),
  -                                                                 l_on_cseq:get_range(L2)));
  -        {fail, not_found} -> ?assert(false)
  +            ?equals(l_on_cseq:get_range(L2_),
  +                    intervals:union(l_on_cseq:get_range(L1),
  +                                    l_on_cseq:get_range(L2)));
  +        {fail, not_found} -> ?ct_fail("{fail, not_found}", [])
       end,
       true.
   
  
positive.code:         {merge, success, _L2, _L1} -> ok
      end,
      % no renews during merge!
      ?assert(1 =:= mockup_l_on_cseq:get_renewal_counter()),
      % check L1
      case l_on_cseq:read(l_on_cseq:get_id(L1)) of
          {ok, L1_} -> ?assert(L1_ =:= prbr_bottom);
          {fail, not_found} -> ?assert(false)
      end,
      % check L2
      case l_on_cseq:read(l_on_cseq:get_id(L2)) of
          {ok, L2_} ->
              ?assert(l_on_cseq:get_range(L2_) =:= intervals:union(l_on_cseq:get_range(L1),
                                                                   l_on_cseq:get_range(L2)));
          {fail, not_found} -> ?assert(false)
      end,
      true.
  
  
negative.code:     % check L1
      case l_on_cseq:read(l_on_cseq:get_id(L1)) of
          {ok, L1_} ->
              ?equals(l_on_cseq:get_range(L1_), R1),
              ?equals(l_on_cseq:get_aux(L1_), empty),
              true;
          {fail, not_found} ->
              ?ct_fail("{fail, not_found}", [])
      end,
      % check L2
      case l_on_cseq:read(l_on_cseq:get_id(L2)) of
          {ok, L2_} ->
              ?equals(l_on_cseq:get_range(L2_), R2),
              ?equals(l_on_cseq:get_aux(L2_), empty),
              true;
          {fail, not_found} ->
              ?ct_fail("{fail, not_found}", [])
      end,
      LeaseList = mockup_l_on_cseq:get_lease_list(),
      ActiveLease = lease_list:get_active_lease(LeaseList),
      [PassiveLease] = lease_list:get_passive_leases(LeaseList),
      ?equals(l_on_cseq:get_id(ActiveLease), l_on_cseq:get_id(L2)),
      ?equals(l_on_cseq:get_id(PassiveLease), l_on_cseq:get_id(L1)),
      true.
  
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  