Commit best block after closing transaction (#1791)

ethcore/src/tests/helpers.rs

@@ -261,6 +261,7 @@ pub fn generate_dummy_blockchain(block_number: u32) -> GuardedTempResult<BlockCh
 	let batch = db.transaction();
 	for block_order in 1..block_number {
 		bc.insert_block(&batch, &create_unverifiable_block(block_order, bc.best_block_hash()), vec![]);
+		bc.commit();
 	}
 	db.write(batch).unwrap();
 
@@ -279,6 +280,7 @@ pub fn generate_dummy_blockchain_with_extra(block_number: u32) -> GuardedTempRes
 	let batch = db.transaction();
 	for block_order in 1..block_number {
 		bc.insert_block(&batch, &create_unverifiable_block_with_extra(block_order, bc.best_block_hash(), None), vec![]);
+		bc.commit();
 	}
 	db.write(batch).unwrap();