def test_if_the_blocks_are_not_changed_then_chain_should_be_a_valid_chain():
chain = Blockchain()
block_id_zero = Block()
block_id_one = Block()
block_id_two = Block()
chain.add_block(block_id_zero)
first_validation = chain.validate()
assert first_validation == True
chain.add_block(block_id_one)
second_validation = chain.validate()
assert second_validation == True
chain.add_block(block_id_two)
third_validation = chain.validate()
assert third_validation == True
def test_if_a_block_is_changed_then_chain_should_not_be_a_valid_chain():
chain = Blockchain()
block_id_zero = Block()
block_id_one = Block()
block_id_two = Block()
chain.add_block(block_id_zero)
chain.add_block(block_id_one)
chain.add_block(block_id_two)
block_id_one.data = {'hacked'}
block_id_one.calculate_hash()
validation = chain.validate()
assert validation == False
