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Lab Workbook - Test Driven Development

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The notation that follows every question denotes the level on the

Revised Bloom's Taxonomy.

Lab - 1

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  1. Write a stub function for calculating the LCM of two numbers.

                                                            - U-level

  2. Write the tests for the LCM function, place the tests in if

     __name__ == '__main__': part of the Python file. Demonstrate that

     the tests fail.                                        - U-level

  3. Implement the code for the LCM function, using the gcd function

     provided in the examples in the chapter. Demonstrate the tests

     pass. (For the algorithm refer to Wikipedia - [0])     - Ap-level

  4. Alternatively, build a set of test cases, preferably a large

     number of cases, place it in a text file and use these test cases

     to test your LCM function. Demonstrate that tests still continue

     to pass.                                               - U-level

[0] - http://en.wikipedia.org/wiki/Least_common_multiple#Reduction_by_the_greatest_common_divisor

Lab - 2

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  1. Write the stub function, followed by the tests(demonstrating the

     failed tests), in turn followed by the code(demonstrating the

     passing tests) to calculate the number of days between two

     dates. Name your function num_of_days(). The function should take

     two arguments, both being tuples. Each tuple represents the date

     in the format of (dd, mm, yyyy) where dd, mm and yyyy are

     integers.                                              - Ap-level

  2. Rewrite the num_of_days() function to take the start date as an

     optional argument. If the start date is not specified calculate

     the number of days between the only specified date since Unix

     epoch. Prior to manipulating the code to do this, make sure you

     change the tests, make them fail and then refactor the code.

                                                            - Ap-level

Lab -3

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  1. Move the tests that were written to GCD function in the examples

     of this chapter to a separate function called test_gcd(). Do the

     same for LCM function and num_of_days() function. Make sure when

     the respective Python files are executed as stand alone scripts

     these tests executed.                                  - U-level

  2. Put all these files in a single directory called utils and run

     the nosetests command. Make a report of the results.   - U-level

  3. Write doctests to each of the above functions. Demonstrate and

     report the results as executed by running the doctests using

     doctest.testmod() function and using nosetests command. -Ap-level

Lab - 4

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  1. Consider the following use case: We are given a large list of

     items called *data* where each item is a again a list with three

     values: username, which is a string; status of the user which

     can be one of the following three strings 'new', 'valid' or

     'invalid'; and the last login time which is a datetime Python

     object.  Write a function called **query** that takes a filter

     dictionary as a parameter and returns the result of the items in

     the *data* list. They keys of the dictionary can be 'user',

     'status' and 'logtime' and their corresponding values can be any

     of the valid values for the corresponding key. Example filter

     dictionary::

       filter = {

           'user': 'john'

           'status': 'new'

           }

     Place your function in a file called query.py. Before writing the

     actual function, follow the test driven development

     approach. First write a stub, fail the tests and then write the

     code and make sure the tests pass. Specifically use unittest

     framework to test this function. Place your tests in a file

     called test_query.py

     A developer wrote a small utility function in a file named

     user_utils.py which uses your **query** function which looks as

     follows::

       def login_util(user=None):

           """Takes a user name and returns his last login time if the

           user is a valid user, else return None. If the user is

           'host' it returns the last login time of all the users.

           """

           filter_dict = {

               'user': user

               'status': 'active'

               }

           if user == 'host':

               filter_dict['status'] + ['new', 'invalid']

           return query(filter_dict)

     Unfortunately the developer did not provide us with the test

     cases. We wrote the following test cases for you to only discover

     that the function miserably fails. 

     The tests were placed in a file called test_user_utils.py and we

     have used the unittest framework::

       import query

       import user_utils

       import unittest

       class TestUserUtils(unittest.TestCase):

           def setUp(self):

               """Boiler plate method to provide common data to all

               the test methods.

               """

               self.test_names = ['Alex', 'Guido', 'Thomas', 'host',

                   'Tom', 'James']

               self.data_len = len(query.data)

           def test_login_utils(self):

               """Tests for the login_utils function.

               """

               for name in self.test_names:

                   if name == 'host':

                       assertEqual(len(user_utils.login_utils(name)), self.data_len)

                   else:

                       assertLess(len(user_utils.login_utils(name)), self.data_len)

           def tearDown(self):

               """Boiler plate method to clean up all the data created

               for tests.

               """

               del self.test_names

               del self.data_len

     Fix the bug, run the tests to make sure the function passes the

     tests and if possible refactor the code with a better approach. - An-level