When you write a function or a class, you can also write tests for that code. Testing proves that your code works as it’s supposed to in response to all the input types it’s designed to receive. When you write tests, you can be confident that your code will work correctly as more people begin to use your programs. You’ll also be able to test new code as you add it to make sure your changes don’t break your program’s existing behavior. Every programmer makes mistakes, so every programmer must test their code often, catching problems before users encounter them.
TRY IT YOURSELF #1
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.
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.
TRY IT YOURSELF #2
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.