Intro to Unit Testing and Continuous Integration

Presented at PyOhio 2022.

Having unit tests and continuous integration (CI) as part of your development are considered best practises. But how do these things work? In this talk, we will cover the benefits of writing unit tests and how to get started with it in Python. Then, we'll step it up running tests as part CI. And that's not all! CI is not just about running tests, but for other things as well, like code quality checks, and even building and generating documentation.

Transcript

1. Intro to Unit Testing and Continuous Integration Mariatta Wijaya Senior Developer Relations Engineer @ Google Python Core Developer @mariatta PyOhio 2022
2. Unit Testing
3. Unit Testing tldr; do it
4. Why Unit Test? def add_two_numbers(first, second): """Adds up both numbers and return the sum.""" return first + second To answer: “Does the code work?” >>> print(add_two_numbers(1, 2)) 3 add_number.py @mariatta
5. Why Unit Test? To answer: “Does the code work?” import unittest from add_number import add_two_numbers class TestAddNumbers(unittest.TestCase): def test_add_two_numbers(self): result = add_two_numbers(1, 2) self.assertEqual(result, 3) test_add_number.py >>> python -m unittest test_add_number . ---------------------------------------------------------------------- Ran 1 test in 0.000s OK @mariatta
6. Why Unit Test? Test your code against various inputs and scenarios def test_add_two_numbers(self): result = add_two_numbers(1, 2) self.assertEqual(result, 12) >>> python -m unittest test_add_number F ====================================================================== FAIL: test_add_two_numbers (test_add_number.TestAddNumbers) ---------------------------------------------------------------------- Traceback (most recent call last): File "test_add_number.py", line 9, in test_add_two_numbers self.assertEqual(result, 12) AssertionError: 3 != 12 ---------------------------------------------------------------------- Ran 1 test in 0.000s FAILED (failures=1) @mariatta
7. Why Unit Test? Test your code against various inputs and scenarios def test_add_two_numbers(self): result = add_two_numbers(1, 2) self.assertEqual(result, 3) def test_add_two_negative_numbers(self): result = add_two_numbers(-1, -2) self.assertEqual(result, -3) def test_add_decimals_numbers(self): result = add_two_numbers(10.5, 3.25) self.assertEqual(result, 13.75) @mariatta
8. Why Unit Test? Find bugs early def test_add_letters(self): result = add_two_numbers(“A”, “B”) self.assertEqual(result, “AB”) @mariatta
9. Why Unit Test? Find bugs early def test_add_letters(self): result = add_two_letters(“A”, “B”) self.assertEqual(result, “AB”) def test_add_letter_and_number(self): result = add_two_numbers(1, “B”) self.assertEqual( ) @mariatta
10. Why Unit Test? Find bugs early def add_two_numbers(first, second): """Adds up both numbers and return the sum. Input values must be numbers.""" if not isinstance(first, (int, float)) \ or not (isinstance(second, (int, float))): raise ValueError("Inputs must be numbers.") return first + second @mariatta
11. Why Unit Test? Find bugs early def add_two_numbers(first, second): """Adds up both numbers and return the sum. Input values must be numbers.""" if not isinstance(first, (int, float)) \ or not (isinstance(second, (int, float))): raise ValueError("Inputs must be numbers.") return first + second def test_add_letters(self): with self.assertRaises(ValueError): add_two_numbers("A", "B") def test_add_letter_and_number(self): with self.assertRaises(ValueError): add_two_numbers(1, "B") @mariatta
12. Why Unit Test? Provides documentation and code example def test_add_two_numbers(self): ... def test_add_two_negative_numbers(self): ... def test_add_decimals_numbers(self): ... def test_add_letters(self): """Will raise error, only numbers allowed.""" @mariatta
13. Why Unit Test? Facilitate future modification Compatibility against different Python/library version >>> python3.9 -m unittest test_add_number >>> python3.10 -m unittest test_add_number >>> python3.11 -m unittest test_add_number @mariatta
14. Why Unit Test? Facilitate future modification Catch deprecation warnings >>> python3.9 -Wd -m unittest test_add_number DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated since Python 3.3, and in 3.10 it will stop working from collections import Mapping # Deprecated in Python 3.10 @mariatta
15. Why Unit Test? Continuous Integration (CI) The practice of using automation to frequently integrating (aka merging) code changes from various contributors into a single project. @mariatta
16. Continuous Integration
17. Continuous Integration tldr; do it
18. Why CI Does the code work? Integrating Code is Costly (and Risky) Does it do what it’s supposed to do? What are the constraints? Does it handle exceptions? Is it compatible with the rest of the software? @mariatta
19. Merging Code Without CI 1 Get a copy of the code to be merged 2 Set up local environments to test the code 3 Run the tests @mariatta
20. Merging Code with CI 1 Get a copy of the code to be merged 2 Set up local environments to test the code 3 Run the tests automatically automatically automatically @mariatta
21. Merging Code with CI @mariatta
22. Adding CI GitHub Actions (https://github.com/features/actions) GitLab Pipelines (https://docs.gitlab.com/pipelines) Circle CI (https://circleci.com) Travis CI (https://travis-ci.org) etc @mariatta
23. GitHub Actions Docs: https://github.com/features/actions Configured by adding a YAML file on your repo under .github/workflows directory The YAML file contains a set of instructions to tell the CI how to run the tests. @mariatta
24. GitHub Actions Example Repo: https://github.com/Mariatta/sample_ci_repo jobs: test: name: test w/ Python ${{ matrix.python-version }} runs-on: ubuntu-latest strategy: matrix: python-version: ["3.9", “3.10"] steps: - uses: actions/checkout@v2 - name: Install Dependencies run: python3 -m pip install -U pip coverage - name: Run Tests run: python -m unittest test_add_number .github/wofklows/ci.yml Running Unittest @mariatta
25. GitHub Actions Example Repo: https://github.com/Mariatta/sample_ci_repo jobs: test: name: test w/ Python ${{ matrix.python-version }} runs-on: ubuntu-latest strategy: matrix: python-version: ["3.9", “3.10"] steps: - uses: actions/checkout@v2 - name: Install Dependencies run: python3 -m pip install -U pip coverage - name: Run Tests run: python -m unittest test_add_number .github/wofklows/ci.yml Running Unittest @mariatta
26. GitHub Actions Example Repo: https://github.com/Mariatta/sample_ci_repo jobs: test: name: test w/ Python ${{ matrix.python-version }} runs-on: ubuntu-latest strategy: matrix: python-version: ["3.9", “3.10"] steps: - uses: actions/checkout@v2 - name: Install Dependencies run: python3 -m pip install -U pip coverage - name: Run Tests run: python -m unittest test_add_number .github/wofklows/ci.yml Running Unittest @mariatta
27. GitHub Actions Example Repo: https://github.com/Mariatta/sample_ci_repo jobs: test: name: test w/ Python ${{ matrix.python-version }} runs-on: ubuntu-latest strategy: matrix: python-version: ["3.9", “3.10"] steps: - uses: actions/checkout@v2 - name: Install Dependencies run: python3 -m pip install -U pip coverage - name: Run Tests run: python -m unittest test_add_number .github/wofklows/ci.yml Running Unittest @mariatta
28. GitHub Actions Example Repo: https://github.com/Mariatta/sample_ci_repo jobs: black-formatting: name: code autoformatting with black runs-on: ubuntu-latest steps: - uses: actions/checkout@v2 - name: Install Dependencies run: python3 -m pip install -U pip black - name: Check code with black run: black --check ./ .github/wofklows/ci.yml Check Code Style @mariatta
29. GitHub Actions Example Repo: https://github.com/Mariatta/sample_ci_repo jobs: code-coverage: name: Code coverage runs-on: ubuntu-latest steps: - uses: actions/checkout@v2 - name: Install Dependencies run: python3 -m pip install -U pip coverage - name: Run test and produce coverage report run: | coverage run test_add_number.py coverage report .github/wofklows/ci.yml Check Code Coverage @mariatta
30. GitHub Actions Example Repo: https://github.com/Mariatta/sample_ci_repo @mariatta
31. Advanced Topics on Testing unittest module documentation https://docs.python.org/3/library/unittest.html @mariatta Python Tutorial: Unit Testing Your Code with the unittest Module, by Corey Schafer https://youtu.be/6tNS--WetLI Getting Started With Testing in Python, Real Python https://realpython.com/python-testing/
32. Advanced Topics on Testing mock object library https://docs.python.org/3/library/unittest.mock.html @mariatta Mocking Understanding the Python Mock Object Library, Real Python https://realpython.com/python-mock-library/ Demystifying the Patch Function, PyCon US talk by Lisa Roach https://www.youtube.com/watch?v=ww1UsGZV8fQ
33. Advanced Topics on Testing pytest framework: https://docs.pytest.org/ @mariatta Introduction to Unit Testing in Python with Pytest, PyCon US Tutorial by Michael Tom-Wing and Christie Wilson https://youtu.be/UPanUFVFfzY pytest
34. Advanced Topics on Testing @mariatta End-to-end Testing Testing the workflow of your software application from start to finish. What is End-to-End Testing and When Should You Use It?, freeCodeCamp https://www.freecodecamp.org/news/end-to-end-testing-tutorial/ Selenium with Python https://selenium-python.readthedocs.io/
35. Unit Testing & CI do it
36. THANK YOU 31 @mariatta