Testing

Will Weaver

What I Mean by Testing?

• Automatic and repeatable checking that code written works as expected.

• Correct result

• Correct side effects

• Speedy enough

• Writing tests prior to writing code

Why Test?

• Reduce regression bugs

• Increase code quality

• Better design

• Find problems early

• Helps you know when you are done coding

Levels of Testing

• Unit

• Integration

• System / End-to-End

• Acceptance

Unit Testing

• Testing small units

• Test all cases / scenarios

• Mock / Patch external calls

Unit Test Example

1 # transaction.py 2 class Transaction(object): 3 4 def __init__(self, action, amount): 5 self.action = action 6 self.amount = amount 7 8 9 # bank_account.py10 class BankAccount(object):11 12 def __init__(self, initial_balance=0):13 self.balance = initial_balance14 self.transactions = [Transaction('initial', initial_balance)]

Unit Test Example (cont'd)17 # test_bank_account.py

18 class DescribeBankAccount(BaseTestCase):19 20 # Arrange21 @classmethod22 def configure(cls):23 cls.init_balance = 10.024 cls.transaction = cls.create_patch('bank_account.Transaction')25 26 # Act27 @classmethod28 def execute(cls):29 cls.bank_account = BankAccount(cls.init_balance)30 31 # Assert32 def should_have_balance(self):33 self.assertEqual(self.bank_account.balance, self.init_balance)34 35 def should_create_transaction(self):36 self.transaction.assert_called_once_with('initial', self.init_balance)37 38 def should_have_transactions(self):39 self.assertEqual(40 self.bank_account.transactions, [self.transaction.return_value])

Integration Testing

• Test interaction with dependencies / external calls

• Not as detailed as unit tests - no need to test every scenario

• Minimal mocking / patching

Integration Test Example

17 # test_bank_account.py18 class DescribeBankAccount(BaseTestCase):19 20 # Arrange21 @classmethod22 def configure(cls):23 cls.init_balance = 10.024 25 # Act26 @classmethod27 def execute(cls):28 cls.bank_account = BankAccount(cls.init_balance)29 30 # Assert31 def should_have_transactions(self):32 self.assertEqual(33 self.bank_account.transactions,34 [Transaction('initial', self.init_balance)],35 )

System / End-to-End Testing

• Test public endpoints

• Use full stack

• No mocking / patching

• Minimal to no inspecting of underlying side effects - only results of calls

• Run in a staging environment

System Test Example 1 # transaction.py 2 class Transaction(object): 3 4 def __init__(self, action, amount): 5 self.action = action 6 self.amount = amount 7 8 9 # bank_account.py10 class BankAccount(object):11 12 def __init__(self, initial_balance=0):13 self._balance = initial_balance14 self._transactions = [Transaction('initial', initial_balance)]15 16 def deposit(self, amount):17 self._balance += amount18 self._transactions.append(Transaction('deposit', amount))19 20 def withdraw(self, amount):21 self._balance -= amount22 self._transactions.append(Transaction('withdrawal', amount))23 24 def get_transactions(self):25 return self._transactions

System Test Example (cont’d)

28 # test_bank_account.py29 class WhenDepositingToBankAccount(BaseTestCase):30 31 # Arrange32 @classmethod33 def configure(cls):34 cls.bank_account = BankAccount(100.0)35 36 # Act37 @classmethod38 def execute(cls):39 cls.bank_account.deposit(20.0)40 cls.bank_account.deposit(25.0)41 cls.bank_account.withdrawal(10.0)42 cls.bank_account.withdrawal(5.0)43 cls.transactions = cls.bank_account.get_transactions()44 45 # Assert46 def should_have_transactions(self):47 self.assertEqual(len(self.transactions), 5)

Acceptance Testing

• Fulfill user stories

• Can be written and/or manual

• Could be written by someone other than developer - stakeholder

• Full stack

• Run against staging environment

Acceptance Testing Frameworks

• https://pypi.python.org/pypi/behave

• http://robotframework.org/

• A few more found here:https://wiki.python.org/moin/PythonTestingToolsTaxonomy#Acceptance.2FBusiness_Logic_Testing_Tools