pub fn get_test_signed_transaction(
sender: AccountAddress,
sequence_number: u64,
private_key: &Ed25519PrivateKey,
public_key: Ed25519PublicKey,
payload: Option<TransactionPayload>,
expiration_timestamp_secs: u64,
gas_unit_price: u64,
gas_currency_code: String,
max_gas_amount: Option<u64>
) -> SignedTransaction