Prepare Source Code

Please begin by reading the following subsections, Experiment n (where n ranges from 1 to 4). You then return to this section to complete the codebase setup for each section.

1. Go to your GitHub organization created in 4.1 Create AWSome Books Repository.

• Click the dropdown.
• Select New repository.

2. Fill out the following information.

• For Owner, choose fcj-workshops-2024.
• For Repository name, enter experiment-n where n is the experimental subsection you are working on.
• Select Public option.

3. Choose your favorite workspace on your local machine. Clone this remote repository github.com/Definitely-not-AWS-Workshops/get-1s.

git clone https://github.com/Definitely-not-AWS-Workshops/get-1s

Along with the unchanged content of main.py and test.py from the previous section, let’s now get an overview of the CI workflow defined in .github/workflows/ci.yml.

name: CI

on:
  pull_request:

  merge_group:
    branches: [main]

jobs:
  run-test:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v4

      - name: Set up Python
        uses: actions/setup-python@v4
        with:
          python-version: "3.9"

      - name: Extend the workflow duration by an additional 10 seconds.
        run: sleep 10

      - name: Show main.py content
        run: cat main.py

      - name: Show test.py content
        run: cat test.py

      - name: Run tests
        run: python test.py

In general, this workflow is triggered when a pull request is created or when a branch is part of a merge group (main branch). It sets up a CI job on an Ubuntu machine, checks out the code, installs Python 3.9, prints the contents of two files (main.py and test.py) for troubleshooting, and finally runs the test file (test.py) to validate the code changes. The sleep 10 step appears to add a delay, possibly for debugging purposes.

4. Change the directory name to experiment-n where n is the experimental subsection you are working on.

mv get-1s experiment-n

5. Change into the directory experiment-n where n is the experimental subsection you are working on. And then remove the .git folder.

cd experiment-n && rm -rf .git

6. Initialize a new git repository.

git init

7. Link to the remote repository that you have just created with experiment-n where n is the experimental subsection you are working on

git remote add origin https://github.com/fcj-workshops-2024/experiment-n.git

8. Make your first commit and push to the remote repository.

git add . && git commit -m "first commit" && git push --set-upstream origin main

9. Create and switch to the person-a branch.

git checkout -b person-a

10. In the main.py file, change the default value of the parameter n from DEFAULT to 7.

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DEFAULT=1

- def get_1s(n=DEFAULT):
+ def get_1s(n=7):

    '''
        TODO: return an array of 1s
    '''

    return [1] * n

11. Run the test.

python test.py

It should be successful for your test to run.

12. Make a commit.

git add . && git commit -m "change the default value of the parameter n from DEFAULT to 7"

13. Switch to the main branch.

git checkout main

14. Create and switch to the person-b branch.

git checkout -b person-b

15. Make a change to main.py file.

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DEFAULT=1

def get_1s(n=DEFAULT):

    '''
        TODO: return an array of 1s
    '''

-   return [1] * n
+   return [1] * (30 if n==DEFAULT else n)

16. Add a test to test.py file.

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import unittest
from main import get_1s

class TestGet1sFunction(unittest.TestCase):
    
    def test_with_10(self):
        """Test the function with 10."""
        result = get_1s(10)
        expected_result = [1] * 10
        self.assertEqual(result, expected_result)

+   def test_with_default(self):
+       """Test the function with default."""
+       result = get_1s()
+       expected_result = [1] * 30
+       self.assertEqual(result, expected_result)

if __name__ == "__main__":
    unittest.main()

17. Run the test.

python test.py

It should be successful for your test to run.

18. Make a commit.

git add . && git commit -m "modify the get_1s return and add another test"

Your code changes on each branch have passed all local tests successfully! However, if either person a or person b merges their changes into the main branch first, and on the other branch you then forget to pull the latest updates from main before running your local tests again, you might run into unexpected issues when creating a pull request and merging back to main.

To investigate, you run a series of experiments to see if your well-tested local code changes could still fail during pull requests, even when there are no visible code conflicts.