1. Testing
Will Weaver

2. What I Mean by Testing?
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Automatic and repeatable checking that code
written works as expected.
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Correct side effects
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Correct result
Speedy enough
Writing tests prior to writing code

3. Why Test?
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Reduce regression bugs
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Increase code quality
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Better design
Find problems early
Helps you know when you are done coding

4. Levels of Testing
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Unit
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Integration
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System / End-to-End
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Acceptance

5. Unit Testing
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Testing small units
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Test all cases / scenarios
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Mock / Patch external calls

6. Unit Test Example
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# transaction.py
class Transaction(object):
def __init__(self, action, amount):
self.action = action
self.amount = amount
# bank_account.py
class BankAccount(object):
def __init__(self, initial_balance=0):
self.balance = initial_balance
self.transactions = [Transaction('initial', initial_balance)]

7. Unit Test Example (cont'd)
17 # test_bank_account.py
18 class DescribeBankAccount(BaseTestCase):
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# Arrange
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@classmethod
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def configure(cls):
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cls.init_balance = 10.0
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cls.transaction = cls.create_patch('bank_account.Transaction')
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# Act
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@classmethod
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def execute(cls):
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cls.bank_account = BankAccount(cls.init_balance)
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# Assert
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def should_have_balance(self):
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self.assertEqual(self.bank_account.balance, self.init_balance)
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def should_create_transaction(self):
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self.transaction.assert_called_once_with('initial', self.init_balance)
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def should_have_transactions(self):
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self.assertEqual(
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self.bank_account.transactions, [self.transaction.return_value])

8. Integration Testing
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Test interaction with dependencies / external
calls
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Not as detailed as unit tests - no need to test
every scenario
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Minimal mocking / patching

9. Integration Test Example
17 # test_bank_account.py
18 class DescribeBankAccount(BaseTestCase):
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# Arrange
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@classmethod
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def configure(cls):
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cls.init_balance = 10.0
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# Act
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@classmethod
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def execute(cls):
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cls.bank_account = BankAccount(cls.init_balance)
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# Assert
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def should_have_transactions(self):
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self.assertEqual(
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self.bank_account.transactions,
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[Transaction('initial', self.init_balance)],
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)

10. System / End-to-End Testing
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Test public endpoints
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Use full stack
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No mocking / patching
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Minimal to no inspecting of underlying side
effects - only results of calls
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Run in a staging environment

11. System Test Example
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# transaction.py
class Transaction(object):
def __init__(self, action, amount):
self.action = action
self.amount = amount
# bank_account.py
class BankAccount(object):
def __init__(self, initial_balance=0):
self._balance = initial_balance
self._transactions = [Transaction('initial', initial_balance)]
def deposit(self, amount):
self._balance += amount
self._transactions.append(Transaction('deposit', amount))
def withdraw(self, amount):
self._balance -= amount
self._transactions.append(Transaction('withdrawal', amount))
def get_transactions(self):
return self._transactions

12. System Test Example (cont’d)
28 # test_bank_account.py
29 class WhenDepositingToBankAccount(BaseTestCase):
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# Arrange
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@classmethod
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def configure(cls):
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cls.bank_account = BankAccount(100.0)
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# Act
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@classmethod
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def execute(cls):
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cls.bank_account.deposit(20.0)
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cls.bank_account.deposit(25.0)
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cls.bank_account.withdrawal(10.0)
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cls.bank_account.withdrawal(5.0)
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cls.transactions = cls.bank_account.get_transactions()
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# Assert
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def should_have_transactions(self):
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self.assertEqual(len(self.transactions), 5)

13. Acceptance Testing
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Fulfill user stories
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Can be written and/or manual
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Could be written by someone other than
developer - stakeholder
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Full stack
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Run against staging environment

14. Acceptance Testing
Frameworks
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https://pypi.python.org/pypi/behave
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http://robotframework.org/
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A few more found here:
https://wiki.python.org/moin/PythonTestingToolsT
axonomy#Acceptance.2FBusiness_Logic_Testin
g_Tools