unittests.py

class Phonebook:
    def __init__(self):
        self.entries = {}
    
    def add(self, name, number):
        self.entries[name] = number
    
    def lookup(self, name):
        return self.entries[name]
        
    def is_consistent(self):
        return True

# --------------------------------------

import unittest

from phonebook import Phonebook

class PhonebookTest(unittest.TestCase):
    
    def setUp(self):
        self.phonebook = Phonebook()
    
    def test_lookup_entry_by_name(self):
        self.phonebook.add("Bob", "12345")
        self.assertEqual("12345", self.phonebook.lookup("Bob"))
        
    def test_missing_entry_raises_KeyError(self):
        with self.assertRaises(KeyError):
            self.phonebook.lookup("missing")
            
    def test_empty_phonebook_is_consistent(self):
        self.assertTrue(self.phonebook.is_consistent())
        
    @unittest.skip("poor example")
    def test_is_consistent(self):
        self.assertTrue(self.phonebook.is_consistent())
        self.phonebook.add("Bob", "12345")
        self.assertTrue(self.phonebook.is_consistent())
        self.phonebook.add("Mary", "012345")
        self.assertTrue(self.phonebook.is_consistent())
        self.phonebook.add("Sue", "12345") # identical to Bob
        self.assertFalse(self.phonebook.is_consistent())
        self.phonebook.add("Sue", "123") # prefix of Bob
        self.assertFalse(self.phonebook.is_consistent())
        
    def test_phonebook_with_normal_entries_is_consistent(self):
        self.phonebook.add("Bob", "12345")
        self.phonebook.add("Mary", "012345")
        self.assertTrue(self.phonebook.is_consistent())

    def test_phonebook_with_duplicate_entries_is_inconsistent(self):
        self.phonebook.add("Bob", "12345")
        self.phonebook.add("Mary", "12345")
        self.assertFalse(self.phonebook.is_consistent())
        
    def test_phonebook_with_numbers_that_prefix_one_another_is_inconsistent(self):
        self.phonebook.add("Bob", "12345")
        self.phonebook.add("Mary", "123")
        self.assertFalse(self.phonebook.is_consistent())
        
    def test_phonebook_adds_names_and_numbers(self):
        self.phonebook.add("Sue", "12345")
        self.assertIn("Sue", phonebook.get_names())
        self.assertIn("12345", phonebook.get_numbers())