test_observer.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import sys
from io import StringIO
from observer import Subject, Data, DecimalViewer, HexViewer

if sys.version_info < (2, 7):
    import unittest2 as unittest
else:
    import unittest

try:
    from unittest.mock import patch
except ImportError:
    from mock import patch


class TestSubject(unittest.TestCase):

    @classmethod
    def setUpClass(cls):
        cls.s = Subject()
        cls.dec_obs = DecimalViewer()
        cls.hex_obs = HexViewer()

    def test_a_observer_list_shall_be_empty_initially(cls):
        cls.assertEqual(len(cls.s._observers), 0)

    def test_b_observers_shall_be_attachable(cls):
        cls.s.attach(cls.dec_obs)
        cls.assertEqual(isinstance(cls.s._observers[0], DecimalViewer), True)
        cls.assertEqual(len(cls.s._observers), 1)
        cls.s.attach(cls.hex_obs)
        cls.assertEqual(isinstance(cls.s._observers[1], HexViewer), True)
        cls.assertEqual(len(cls.s._observers), 2)

    def test_c_observers_shall_be_detachable(cls):
        cls.s.detach(cls.dec_obs)
        # hex viewer shall be remaining if dec viewer is detached first
        cls.assertEqual(isinstance(cls.s._observers[0], HexViewer), True)
        cls.assertEqual(len(cls.s._observers), 1)
        cls.s.detach(cls.hex_obs)
        cls.assertEqual(len(cls.s._observers), 0)

class TestData(unittest.TestCase):

    @classmethod
    def setUpClass(cls):
        cls.dec_obs = DecimalViewer()
        cls.hex_obs = HexViewer()
        cls.sub = Data('Data')
        #inherited behavior already tested with TestSubject
        cls.sub.attach(cls.dec_obs)
        cls.sub.attach(cls.hex_obs)

    def test_data_change_shall_notify_all_observers_once(cls):
        with patch.object(cls.dec_obs, 'update') as mock_dec_obs_update,\
            patch.object(cls.hex_obs, 'update') as mock_hex_obs_update:
            cls.sub.data = 10
            cls.assertEqual(mock_dec_obs_update.call_count, 1)
            cls.assertEqual(mock_hex_obs_update.call_count, 1)

    def test_data_value_shall_be_changeable(cls):
        cls.sub.data = 20
        cls.assertEqual(cls.sub._data, 20)

    def test_data_name_shall_be_changeable(cls):
        cls.sub.name = 'New Data Name'
        cls.assertEqual(cls.sub.name, 'New Data Name')

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