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bank_test.py
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bank_test.py
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from __future__ import print_function
# import platform
import sys
import threading
import time
import unittest
class UnsyncedBankAccount(object):
"""Bank account with no synchronization lock, prone to race condition."""
def __init__(self):
self.is_open = False
self.balance = 0
def get_balance(self):
if self.is_open:
return self.balance
else:
raise ValueError
def open(self):
self.is_open = True
def deposit(self, amount):
if self.is_open and amount > 0:
self.balance += amount
else:
raise ValueError
def withdraw(self, amount):
if self.is_open and 0 < amount <= self.balance:
self.balance -= amount
else:
raise ValueError
def close(self):
self.is_open = False
class SyncedBankAccount(object):
"""Bank account with synchronization strategy, thread-safe."""
def __init__(self):
self.is_open = False
self.balance = 0
self.lock = threading.Lock()
def get_balance(self):
with self.lock:
if self.is_open:
return self.balance
else:
raise ValueError
def open(self):
self.is_open = True
def deposit(self, amount):
with self.lock:
if self.is_open and amount > 0:
self.balance += amount
else:
raise ValueError
def withdraw(self, amount):
with self.lock:
if self.is_open and 0 < amount <= self.balance:
self.balance -= amount
else:
raise ValueError
def close(self):
self.is_open = False
def adjust_balance_concurrently(account):
def transact():
account.deposit(5)
time.sleep(0.001)
account.withdraw(5)
# Greatly improve the chance of an operation being interrupted
# by thread switch, thus testing synchronization effectively.
# Feel free to tweak the parameters below to see their impact.
try:
sys.setswitchinterval(1e-12)
except AttributeError:
# Python 2 compatible
sys.setcheckinterval(1)
threads = []
for _ in range(1000):
t = threading.Thread(target=transact)
threads.append(t)
t.start()
for thread in threads:
thread.join()
class TestBankAccount(unittest.TestCase):
def test_unsynced(self):
account = UnsyncedBankAccount()
account.open()
account.deposit(1000)
for _ in range(10):
adjust_balance_concurrently(account)
self.assertNotEqual(account.balance, 1000)
def test_synced(self):
account = SyncedBankAccount()
account.open()
account.deposit(1000)
for _ in range(10):
adjust_balance_concurrently(account)
self.assertEqual(account.balance, 1000)
if __name__ == '__main__':
unittest.main()
# Initialization
# unsync_account = UnsyncedBankAccount()
# unsync_account.open()
# unsync_account.deposit(1000)
# sync_account = SyncedBankAccount()
# sync_account.open()
# sync_account.deposit(1000)
# Test unsynced bank account
# for _ in range(10):
# adjust_balance_concurrently(unsync_account)
# Test synced bank account
# for _ in range(10):
# adjust_balance_concurrently(sync_account)
# Report results
# print("Python version: {}\n".format(platform.python_version()))
# print("Balance of unsynced account after concurrent transactions:")
# print("{}. Expected: 1000\n".format(unsync_account.balance))
# print("Balance of synced account after concurrent transactions:")
# print("{}. Expected: 1000\n".format(sync_account.balance))