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Solutions - Chapter 11

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11-1: City, Country

Write a function that accepts two parameters: a city name and a country name. The function should return a single string of the form City, Country, such as Santiago, Chile. Store the function in a module called city_functions.py.

Create a file called test_cities.py that tests the function you just wrote (remember that you need to import unittest and the function you want to test). Write a method called test_city_country() to verify that calling your function with values such as santiago and chile results in the correct string. Run test_cities.py, and make sure test_city_country() passes.

city_functions.py:

"""A collection of functions for working with cities."""

def city_country(city, country):
    """Return a string like 'Santiago, Chile'."""
    return f"{city.title()}, {country.title()}"

Note: This is the function we wrote in Exercise 8-6.

test_cities.py:

import unittest

from city_functions import city_country

class CitiesTestCase(unittest.TestCase):
    """Tests for 'city_functions.py'."""

    def test_city_country(self):
        """Does a simple city and country pair work?"""
        santiago_chile = city_country('santiago', 'chile')
        self.assertEqual(santiago_chile, 'Santiago, Chile')

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

Output:

.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK

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11-2: Population

Modify your function so it requires a third parameter, population. It should now return a single string of the form City, Country - population xxx, such as Santiago, Chile - population 5000000. Run test_cities.py again. Make sure test_city_country() fails this time.

Modify the function so the population parameter is optional. Run test_cities.py again, and make sure test_city_country() passes again.

Write a second test called test_city_country_population() that verifies you can call your function with the values 'santiago', 'chile', and 'population=5000000'. Run test_cities.py again, and make sure this new test passes.

Modified city_functions.py, with required population parameter:

"""A collection of functions for working with cities."""

def city_country(city, country, population):
    """Return a string like 'Santiago, Chile - population 5000000'."""
    output_string = f"{city.title()}, {country.title()}"
    output_string += f" -population {population}"
    return output_string

Output from running test_cities.py:

E
======================================================================
ERROR: test_city_country (__main__.CitiesTestCase)
Does a simple city and country pair work?
----------------------------------------------------------------------
Traceback (most recent call last):
  File "pcc\solutions\test_cities.py", line 10, in test_city_country
    santiago_chile = city_country('santiago', 'chile')
TypeError: city_country() missing 1 required positional argument: 'population'

----------------------------------------------------------------------
Ran 1 test in 0.000s

FAILED (errors=1)

Modified city_functions.py, with optional population parameter:

"""A collection of functions for working with cities."""

def city_country(city, country, population=0):
    """Return a string representing a city-country pair."""

    output_string = f"{city.title()}, {country.title()}"
    if population:
        output_string += f" - population {population}"
    return output_string

Output of running test_cities.py:

.
----------------------------------------------------------------------
Ran 1 test in 0.001s

OK

Modified test_cities.py:

import unittest

from city_functions import city_country

class CitiesTestCase(unittest.TestCase):
    """Tests for 'city_functions.py'."""

    def test_city_country(self):
        """Does a simple city and country pair work?"""
        santiago_chile = city_country('santiago', 'chile')
        self.assertEqual(santiago_chile, 'Santiago, Chile')

    def test_city_country_population(self):
        """Can I include a population argument?"""
        santiago_chile = city_country('santiago', 'chile', population=5_000_000)
        self.assertEqual(santiago_chile, 'Santiago, Chile - population 5000000')

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

Output:

..
----------------------------------------------------------------------
Ran 2 tests in 0.000s

OK

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11-3: Employee

Write a class called Employee. The __init__() method should take in a first name, a last name, and an annual salary, and store each of these as attributes. Write a method called give_raise() that adds $5000 to the annual salary by default but also accepts a different raise amount.

Write a test case for Employee. Write two test methods, test_give_default_raise() and test_give_custom_raise(). Use the setUp() method so you don’t have to create a new employee instance in each test method. Run your test case, and make sure both tests pass.

employee.py:

class Employee():
    """A class to represent an employee."""

    def __init__(self, f_name, l_name, salary):
        """Initialize the employee."""
        self.first = f_name.title()
        self.last = l_name.title()
        self.salary = salary

    def give_raise(self, amount=5000):
        """Give the employee a raise."""
        self.salary += amount

test_employee.py:

import unittest

from employee import Employee

class TestEmployee(unittest.TestCase):
    """Tests for the module employee."""

    def setUp(self):
        """Make an employee to use in tests."""
        self.eric = Employee('eric', 'matthes', 65_000)

    def test_give_default_raise(self):
        """Test that a default raise works correctly."""
        self.eric.give_raise()
        self.assertEqual(self.eric.salary, 70000)

    def test_give_custom_raise(self):
        """Test that a custom raise works correctly."""
        self.eric.give_raise(10000)
        self.assertEqual(self.eric.salary, 75000)

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

Output:

..
----------------------------------------------------------------------
Ran 2 tests in 0.000s

OK

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