python-tdd-book/textbook/chap2.md

Chapter 2. Extending Our Functional Test Using the unittest Module

We are trying to build to-do list Django web app

2.1 Using a FT to Scope Out a Minimum Viable App

• Functional Tests = tests that let us see how the app functions from user's perspective
  • It's like a specification for app
  • Tends to track User Story
  • Functional Test == Acceptance Test == End-to-End Test

Steps to create a FT for a MVP/A (Minimum Viable Product/App):

1. Prepare a User Story (e.g. user story for to-do list)
2. Add test assertions along user story, which is expected fail

2.2 Python Standard Library's unittest Module

python's default assert isn't helpful.

The assert keyword is used when debugging code. The assert keyword lets you test if a condition in your code returns True, if not, the program will raise an AssertionError.

unittest module of python standard library can be used

Following are highlights of code snippet shown below:

• tests can be organized into classes, which inherit from unittest.TestCase
• setUp and tearDown are special methods that will be run before/after each test, even test failed
• main body of tests is in test_can_start_a_list_and_retrieve_it_later.
• Any method whose name starts with test is a test method, and will be run by test runner
  • Can have more than one test methods per class.
• Use self.assertIn() instead of assert. More helper functions like assertEqual, assertTrue, and assertFalse are available in unittest
• warning='ignore' suppresses a superfluous ResourceWarning.

class NewVisitorTest(unittest.TestCase):

    def setUp(self):
        self.browser = webdriver.Firefox()

    def tearDown(self):
        self.browser.quit()

    def test_can_start_a_list_and_retrieve_it_later(self):
        ...

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

Hence, a full cycle of test can be executed as it

1. Open Firefox
2. Test title
3. Close Firefox
4. Return test result

Useful TDD Concepts in this chapter

• User Story: A description of how the application will work from the point of view of the user. Used to structure a functional test.
• Expected Failure: When a test fails in the way that we expected it to.