anchor.diff:  
                %% Check highest header.
                ?assertEqual({ok, BH2}, aec_chain:top_header()),
  -             %% Check heighest known block - still genesis.
  +             %% Check highest known block - still genesis.
                ?assertEqual({ok, B0}, aec_chain:top_block()),
   
                %% Check by hash.
  
positive.code: 
                 %% Check highest header.
                 ?assertEqual({ok, BH2}, aec_chain:top_header()),
                 %% Check heighest known block.
                 ?assertEqual({ok, B1}, aec_chain:top_block()),
  
                 %% Check by hash.
  
negative.code: 
                 %% Check highest header.
                 ?assertEqual({ok, BH2}, aec_chain:top_header()),
                 %% Check highest known block.
                 ?assertEqual({ok, B2}, aec_chain:top_block()),
  
                 %% Check by hash.
  