Python mock testing with mockito module

This module is a port of the Mockito mocking framework to Python. Install mockito with easy_install:

easy_install mockito

Suppose you need to test withdraw operation in ATM (file atm.py):

from datetime import datetime

class Atm:
    def signin(self, account):
        self._account = account

    def signout(self):
        self._account = None

    def withdraw(self, amount):
        try:
            self._account.withdraw(amount)
            self._account.comission(amount * 0.005)
        except ValueError:
            self._account.comission(amount * 0.001)
        return self._account.balance(datetime.now())

Here is our test (file mockitoexample.py):

from datetime import datetime
from atm import Atm
import unittest
from mockito import Mock, when, verify, any, verifyNoMoreInteractions

class TestAtm(unittest.TestCase):

    def setUp(self):
        self._mock_account = Mock()
        self._atm = Atm()
        self._atm.signin(self._mock_account)

    def tearDown(self):
        self._atm.signout()
        verifyNoMoreInteractions(self._mock_account)

    def test_withdraw(self):
        # Arrange
        when(self._mock_account).balance(any(datetime))\
                .thenReturn(49.5)

        # Act
        self._mock_account.deposit(150)
        remaining_balance = self._atm.withdraw(100)

        # Assert
        assert remaining_balance == 49.5
        verify(self._mock_account).deposit(150)
        verify(self._mock_account).withdraw(100)
        verify(self._mock_account).comission(0.5)
        verify(self._mock_account).balance(any(datetime))

    def test_withdraw_insufficient_funds(self):
        # Arrange
        when(self._mock_account).withdraw(100)\
                .thenRaise(ValueError('Insufficient funds'))
        when(self._mock_account).balance(any(datetime))\
                .thenReturn(49.9)

        # Act
        self._mock_account.deposit(50)
        remaining_balance = self._atm.withdraw(100)

        # Assert
        assert remaining_balance == 49.9
        verify(self._mock_account).deposit(50)
        verify(self._mock_account).withdraw(100)
        verify(self._mock_account).comission(0.1)
        verify(self._mock_account).balance(any(datetime))

if __name__ == '__main__':
    unittest.main()

Run tests:

python mockitoexample.py

Read more about mockito here.