def test_is_valid_block_jumped_difficulty(last_block, block):
jumped_difficulty = 10
block.difficulty = jumped_difficulty
block.hash = f'{"0" * jumped_difficulty}111abc'
with pytest.raises(Exception,
match='The block difficulty must only adjust by 1'):
Block.is_valid_block(last_block, block)
def test_mined_block_difficulty_limits_at_1():
last_block = Block(time.time_ns(), 'test_last_hash', 'test_hash',
'test_data', 1, 0)
time.sleep(MINE_RATE / SECONDS)
mined_block = Block.mine_block(last_block, 'bar')
assert mined_block.difficulty == 1
def test_slowly_mined_block():
last_block = Block.mine_block(Block.genesis(), 'foo')
time.sleep(
MINE_RATE / SECONDS
) # Delay to ensure it is mined slower than mine_rate, takes argument in second
mined_block = Block.mine_block(last_block, 'bar')
assert mined_block.difficulty == last_block.difficulty - 1
def test_mine_block():
last_block = Block.genesis()
data = 'test-data'
block = Block.mine_block(last_block, data)
assert isinstance(
block, Block
) # Check if the block we created became an instance or object of Block class
assert block.data == data
assert block.last_hash == last_block.hash
assert hex_to_binary(
block.hash)[0:block.difficulty] == '0' * block.difficulty
def is_valid_chain(chain):
'''
Validate the blockchain using following rules
- chain must start with genesis block
- blocks must be formatted correctly
'''
if chain[0].__dict__ != Block.genesis(
).__dict__: # Python can't check equality of two objects, but dictionaries
raise Exception('The genesis block must be valid')
for i in range(1, len(chain)):
block = chain[i]
last_block = chain[i - 1]
Block.is_valid_block(last_block, block)
def test_genesis():
genesis = Block.genesis()
assert isinstance(genesis, Block)
for key, value in GENESIS_DATA.items():
getattr(
genesis, key
) == value # Checks if all values of genesis object are same as that in original dictionary
def from_json(chain_json):
'''
Deserialize a list of serialised blocks into Blockchain object or a chain of Block instances
'''
blockchain = Blockchain()
blockchain.chain = list(
map(lambda block_json: Block.from_json(block_json), chain_json))
return blockchain
def message(self, pubnub, message_object):
print(
f'\n-- Channel: {message_object.channel} | Message: {message_object.message}'
)
if message_object.channel == CHANNELS['BLOCK']:
block = Block.from_json(message_object.message)
potential_chain = self.blockchain.chain[:]
potential_chain.append(block)
try:
self.blockchain.replace_chain(potential_chain)
print('\n --Successfully replaced the local chain')
except Exception as e:
print(f'\n --Did not replace chain: {e}')
elif message_object.channel == CHANNELS['TRANSACTION']:
transaction = Transaction.from_json(message_object.message)
self.transaction_pool.set_transaction(transaction)
print('\n -- Set the new transaction in the transaction pool.')
def test_is_valid_block_bad_block_hash(last_block, block):
block.hash = '000000000000000111abc'
with pytest.raises(Exception, match='The block hash must be correct'):
Block.is_valid_block(last_block, block)
def add_block(self, data):
self.chain.append(Block.mine_block(self.chain[-1], data))
def test_is_valid_block_bad_proof_of_work(last_block, block):
block.hash = 'fff'
with pytest.raises(Exception,
match='The proof of work requirement not met'):
Block.is_valid_block(last_block, block)
def test_is_valid_block_bad_last_hash(last_block, block):
block.last_hash = 'evil_last_hash'
with pytest.raises(
Exception, match='The block last hash must be correct'
): # Tells python that we are expecting this part of code to raise an exception with given exception message
Block.is_valid_block(last_block, block)
def test_is_valid_block(last_block, block):
Block.is_valid_block(last_block, block)
def block(last_block):
return Block.mine_block(last_block, 'test_data')
def last_block():
return Block.genesis()
def __init__(self):
self.chain = [Block.genesis()]
def test_quickly_mined_block():
last_block = Block.mine_block(Block.genesis(), 'foo')
mined_block = Block.mine_block(last_block, 'bar')
assert mined_block.difficulty == last_block.difficulty + 1