DevOps Workshop: Introduction to CI with GitHub Actions

Welcome! In this hands-on workshop you will set up a Continuous Integration (CI) pipeline using GitHub Actions. By the end you will understand how automated testing works in a real development workflow.

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Prerequisites

• A GitHub account
• Git installed on your machine
• Python 3.10+ installed
• A code editor (VS Code recommended)

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Step 1 — Fork & Clone the Repository

1. Click Fork in the top-right corner of this repo on GitHub.
2. Clone your fork locally:

git clone https://github.com/<your-username>/DevopsWorkshop.git
cd DevopsWorkshop

3. Install the test dependency:

pip install -r requirements.txt

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Step 2 — Explore the Codebase

Take a few minutes to look through the project. Here is the structure:

DevopsWorkshop/
├── app/
│   ├── calculator.py      # Basic math functions
│   └── string_utils.py    # String helper functions
├── tests/
│   ├── test_calculator.py # Tests for calculator
│   └── test_string_utils.py # Tests for string utils
├── requirements.txt       # Python dependencies
└── README.md              # You are here!

Tasks:

• Open app/calculator.py and read through the functions.
• Open app/string_utils.py and read through the functions.
• Open the test files in tests/ and see what is being tested.

Question for the group: What do you think the tests are checking? Can you spot anything that might be wrong in the code?

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Step 3 — Run the Tests Locally

Before setting up CI, run the tests on your own machine:

python3 -m pytest tests/ -v

You should see output like this:

tests/test_calculator.py::test_add PASSED
tests/test_calculator.py::test_subtract FAILED
tests/test_calculator.py::test_multiply PASSED
tests/test_calculator.py::test_divide PASSED
tests/test_calculator.py::test_divide_by_zero PASSED
tests/test_calculator.py::test_percentage PASSED
tests/test_string_utils.py::test_reverse_string FAILED
tests/test_string_utils.py::test_capitalize_words PASSED
tests/test_string_utils.py::test_count_vowels FAILED
tests/test_string_utils.py::test_is_palindrome PASSED

Tasks:

• Run the tests. How many pass? How many fail?
• Read the failure messages carefully. Which functions have bugs?

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Step 4 — Create a GitHub Actions Workflow

Now let's automate these tests so they run every time code is pushed.

4a. Create the workflow directory

mkdir -p .github/workflows

4b. Create the workflow file

Create a new file at .github/workflows/ci.yml and paste the following:

name: CI

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

jobs:
  test:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout code
        uses: actions/checkout@v4

      - name: Set up Python
        uses: actions/setup-python@v5
        with:
          python-version: "3.12"

      - name: Install dependencies
        run: pip install -r requirements.txt

      - name: Run tests
        run: python3 -m pytest tests/ -v

Tasks:

• Create the .github/workflows/ directory.
• Create ci.yml with the content above.
• Read through the YAML. Can you identify what each section does?

Discussion:

• on: — When does this workflow run?
• runs-on: — Where does it run?
• steps: — What does each step do?

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Step 5 — Push and Watch the Pipeline Run

Commit your workflow file and push it:

git add .github/workflows/ci.yml
git commit -m "Add CI workflow"
git push origin main

Tasks:

• Go to your repository on GitHub.
• Click the Actions tab.
• Watch the workflow run. Does it pass or fail?

You should see the pipeline fail — because there are three bugs: count_vowels and reverse_string in string_utils.py, and subtract in calculator.py. This is CI doing its job: catching bugs automatically!

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Step 6 — Fix the Bug and See the Pipeline Go Green

Time to fix the bugs! There are three to find:

Bug 1 — count_vowels in app/string_utils.py

1. Find the count_vowels function.
2. Look at the vowel list — what is missing?

💡 Hint (click to reveal)

The vowel string "aeio" is missing "u". It should be "aeiou".

Bug 2 — reverse_string in app/string_utils.py

1. Find the reverse_string function.
2. Look at the slice notation — is it actually reversing the string?

💡 Hint (click to reveal)

The slice s[::1] just returns the string as-is. It should be s[::-1] (note the negative step) to reverse it.

Bug 3 — subtract in app/calculator.py

1. Find the subtract function.
2. Look at the operator — is it subtracting?

💡 Hint (click to reveal)

The function uses + instead of -. It should be return a - b.

5. Run the tests locally to confirm they all pass:

python3 -m pytest tests/ -v

6. Commit and push the fix:

git add app/string_utils.py app/calculator.py
git commit -m "Fix bugs in subtract, reverse_string, and count_vowels"
git push origin main

Tasks:

• Fix the bugs in count_vowels, reverse_string, and subtract.
• Verify all 10 tests pass locally.
• Push the fix and watch the Actions tab go green!

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Bonus Challenges

If you finish early, try these:

Bonus 1 — Add a New Function and Test

Add a new function to app/calculator.py (e.g., power(base, exp)) and write a test for it in tests/test_calculator.py. Push and watch CI run your new test.

Bonus 2 — Create a Pull Request Workflow

Instead of pushing directly to main:

1. Create a new branch: git checkout -b add-power-function
2. Make your changes and push the branch.
3. Open a Pull Request on GitHub.
4. See how CI runs automatically on the PR before merging!

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Key Takeaways

• CI (Continuous Integration) automatically runs tests when code changes.
• GitHub Actions lets you define CI pipelines as YAML files in your repo.
• A failing pipeline tells you something is wrong before it reaches production.
• Fixing a bug and seeing the pipeline go green is the core CI feedback loop.

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Quick Reference

Command	What it does
python3 -m pytest tests/ -v	Run all tests with verbose output
git add <file>	Stage a file for commit
git commit -m "message"	Create a commit
git push origin main	Push to GitHub
git checkout -b <branch>	Create and switch to a new branch

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