adjust block/uncle reward tests and add methods to pkg/geth blockchain and ethclient for direct fetching of eth balances

pkg/core/blockchain.go

@@ -26,6 +26,7 @@ import (
 
 type BlockChain interface {
 	ContractDataFetcher
+	AccountDataFetcher
 	GetBlockByNumber(blockNumber int64) (Block, error)
 	GetEthLogsWithCustomQuery(query ethereum.FilterQuery) ([]types.Log, error)
 	GetHeaderByNumber(blockNumber int64) (Header, error)
@@ -39,3 +40,7 @@ type BlockChain interface {
 type ContractDataFetcher interface {
 	FetchContractData(abiJSON string, address string, method string, methodArgs []interface{}, result interface{}, blockNumber int64) error
 }
+
+type AccountDataFetcher interface {
+	GetAccountBalance(address common.Address, blockNumber *big.Int) (*big.Int, error)
+}

pkg/core/eth_client.go

@@ -32,4 +32,5 @@ type EthClient interface {
 	HeaderByNumber(ctx context.Context, number *big.Int) (*types.Header, error)
 	TransactionSender(ctx context.Context, tx *types.Transaction, block common.Hash, index uint) (common.Address, error)
 	TransactionReceipt(ctx context.Context, txHash common.Hash) (*types.Receipt, error)
+	BalanceAt(ctx context.Context, account common.Address, blockNumber *big.Int) (*big.Int, error)
 }