def test_calculate_balance():
blockchain = Blockchain()
wallet = Wallet()
assert Wallet.calculate_balance(blockchain,
wallet.address) == STARTING_BALANCE
amount = 50
transaction = Transaction(wallet, 'recipient', amount)
blockchain.add_block([transaction.to_json()])
assert Wallet.calculate_balance(
blockchain, wallet.address) == STARTING_BALANCE - amount
received_amount_1 = 25
received_transaction_1 = Transaction(Wallet(), wallet.address,
received_amount_1)
received_amount_2 = 77
received_transaction_2 = Transaction(Wallet(), wallet.address,
received_amount_2)
blockchain.add_block(
[received_transaction_1.to_json(),
received_transaction_2.to_json()])
assert Wallet.calculate_balance(blockchain, wallet.address) == \
STARTING_BALANCE - amount + received_amount_1 + received_amount_2
def is_valid_transaction_chain(chain):
"""
Enforce the rules of a chain composed of blocks of transactions:
- Each transaction must only appear once in the chain.
- There can only be one mining reward per block.
- Each transaction must be valid.
"""
transaction_ids = set()
for i in range(len(chain)):
block = chain[i]
has_mining_reward = False
for transaction_json in block.data:
transaction = Transaction.from_json(transaction_json)
if transaction.id in transaction_ids:
raise Exception(
f'Transaction {transaction.id} is not unique.')
transaction_ids.add(transaction.id)
if transaction.input == MINING_REWARD_INPUT:
if has_mining_reward:
raise Exception('There can only be one mining reward per block. '\
f'Check block with hash: {block.hash}')
has_mining_reward = True
else:
historic_blockchain = Blockchain()
historic_blockchain.chain = chain[0:i]
historic_balance = Wallet.calculate_balance(
historic_blockchain, transaction.input['address'])
if historic_balance != transaction.input['amount']:
raise Exception(f'Transaction {transaction.id} has an invalid '\
'input amount')
Transaction.is_valid_transaction(transaction)