anchor.diff:        {"Insert header meant to be successor of top header - case wrong previous hash",
          fun() ->
                  %% Check chain is at genesis.
  -               B0 = fake_genesis_block(),
  +               B0 = genesis_block(),
                  BH0 = aec_blocks:to_header(B0),
                  ?assertEqual({ok, BH0}, aec_chain:top_header()),
   
  
positive.code: %% Cover unhappy paths not covered in any other tests.
  unhappy_paths_test_() ->
      {foreach,
       fun() -> {ok, Pid} = aec_chain:start_link(fake_genesis_block()), Pid end,
       fun(_ChainPid) -> ok = aec_chain:stop() end,
       [{"Get header by hash - case not found",
         fun() ->
                 %% Check chain is at genesis.
                 B0 = fake_genesis_block(),
                 BH0 = aec_blocks:to_header(B0),
                 ?assertEqual({ok, BH0}, aec_chain:top_header()),
  
  
negative.code: 
  header_chain_test_() ->
      {setup,
       fun() -> {ok, Pid} = aec_chain:start_link(genesis_block()), Pid end,
       fun(_ChainPid) -> ok = aec_chain:stop() end,
       fun() ->
               %% Check chain is at genesis.
               B0 = genesis_block(),
               BH0 = aec_blocks:to_header(B0),
               ?assertEqual({ok, BH0}, aec_chain:top_header()),
  
  