Initialization of system account within unit tests

Question

I check system account resources just after test initialization start. And i see that ram_usage is already 62206 bytes. Where is this bytes come from?

eosio_system_tester.hpp

...
template<typename Lambda>
eosio_system_tester(Lambda setup) {

   using eosio::chain::resource_limits::resource_usage_object;
   using eosio::chain::resource_limits::by_owner;
   const auto& usage  = control->db().get<resource_usage_object,by_owner>( config::system_account_name );
   // Here. usage.ram_usage is 62206 bytes.

   setup(*this);
...

Thanks

Answer 1

Found the answer.

It is genesis block initialization (mostly by eosio.bios.wast).