Add continuous integration episode

config.yaml

@@ -58,17 +58,18 @@ contact: '[email protected]'
 # - another-learner.md
 
 # Order of episodes in your lesson
-episodes: 
-- testing.md
+episodes:
+- 3-testing.md
+- 4-ci.md
 
 # Information for Learners
-learners: 
+learners:
 
 # Information for Instructors
-instructors: 
+instructors:
 
 # Learner Profiles
-profiles: 
+profiles:
 
 # Customisation ---------------------------------------------
 #

episodes/4-ci.md

@@ -0,0 +1,181 @@
+---
+title: Continuous Integration
+teaching: 30
+exercises: 45
+---
+
+:::::::::::::::::::::::::::::::::::::: questions 
+
+- How can we implement automatic testing each time we push changes to the repository?
+
+
+::::::::::::::::::::::::::::::::::::::::::::::::
+
+::::::::::::::::::::::::::::::::::::: objectives
+
+- Set up Continuous Integration using GitHub Actions
+
+::::::::::::::::::::::::::::::::::::::::::::::::
+
+## Introducing Continuous integration
+Follow [these slides](https://lyashevska.github.io/ds-cr-slides/ci/) to understand 
+the basics of continuous integration.
+
+## Full-cycle collaborative workflow
+
+::: challenge 
+
+### Exercise: Full-cycle collaborative workflow
+
+The exercise takes 30-40 minutes.
+
+In this exercise, everybody will:
+
+- A. Set up automated tests with GitHub Actions
+- B. Make test fail / find a bug in their repository
+- C. Open an issue in their repository
+- D. Then each one will clone the repo of one of their exercise partners, fix the bug, and open a pull request (GitHub)
+- E. Everybody then merges their co-worker’s change
+
+
+#### Step 1: Create a new repository on GitHub
+
+- Select a different repository name than your colleagues (otherwise forking the same name will be strange)
+- Before you create the repository, select “Initialize this repository with a README” (otherwise you try to clone an empty repo).
+- Share the repository URL with your exercise group via shared document or chat
+
+#### Step 2: Clone your own repository, add code, commit, and push
+
+Clone the repository.
+
+Add a file `example.py` containing:
+
+```python
+def add(a, b):
+    return a + b
+
+def subtract(a, b):
+    return a + b  # do not change this line until prompted to do so.
+```
+
+Write a test function `def test_add()` for `add` to check that this function is working properly. Do NOT add a test function for `subtract` (yet).
+Run pytest to ensure it works 
+
+Then stage the file (`git add <filename>`), commit (`git commit -m "some commit message"`),
+and push the changes (`git push`).
+
+
+#### Step 3: Enable automated testing
+
+In this step we will enable GitHub Actions.
+- Select "Actions" from your GitHub repository page. You get to a page "Get started with GitHub Actions". 
+- Select the button for "Set up this workflow" under Python Application.
+
+![](fig/ci-python-application-workflow.png)
+Select “Python application” as the starter workflow.
+
+GitHub creates the following file for you in the subfolder `.github/workflows`:
+
+
+```yaml
+# This workflow will install Python dependencies, run tests and lint with a single version of Python
+# For more information see: https://help.github.com/actions/language-and-framework-guides/using-python-with-github-actions
+
+name: Python application
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python 3.9
+      uses: actions/setup-python@v2
+      with:
+        python-version: 3.9
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install flake8 pytest
+        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
+    - name: Lint with flake8
+      run: |
+        # stop the build if there are Python syntax errors or undefined names
+        flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
+        # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
+        flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
+    - name: Test with pytest
+      run: |
+        pytest
+```
+
+
+
+Commit the change by pressing the "Start Commit" button.
+
+#### Step 4: Verify that tests have been automatically run
+
+Observe in the repository how the test succeeds. While the test is executing, the repository has a yellow marker.
+This is replaced with a green check mark, once the test succeeds.
+
+![](fig/ci-tests-succeed-screenshot.png)
+
+Green check means passed.
+
+Also browse the "Actions" tab and look at the steps there and their output.
+
+#### Step 5: Add a test which reveals a problem
+
+After you committed the workflow file, your GitHub repository will be ahead of your local cloned repository. Update your local cloned repository:
+
+```
+$ git pull origin main
+```
+
+Next uncomment add a test function `test_subtract` for to check that the `subtract` function can subtract two numbers from each other, and push it to your remote repository.
+Verify that the test suite now fails on the “Actions” tab (GitHub).
+
+
+#### Step 6: Open an issue on GitHub
+Open a new issue in your repository about the broken test (click the “Issues” button on GitHub and write a title for the issue). The plan is that your colleague will fix the issue through a pull request
+
+#### Step 7: Fork and clone the repository of your colleague
+
+Fork the repository using the GitHub web interface. 
+Make sure you clone the fork after you have forked it. Do not clone your colleague’s repository directly.
+
+
+#### Step 8: Fix the broken test
+
+Fix the function now and run pytest to check that it works.
+Then push to _your fork_. Check whether the action now also passes.
+
+#### Step 9: Open a pull request (GitHub)
+
+Then before accepting the pull request from your colleague, observe how GitHub Actions automatically tested the code.
+
+If you forgot to reference the issue number in the commit message, you can still add it to the pull request: 
+`my pull request title, closes #NUMBEROFTHEISSUE`
+
+#### Step 10
+
+Observe how accepting the pull request automatically closes the issue (provided the commit message or the pull request contained the correct issue number).
+
+Discuss whether this is a useful feature. And if it is, why do you think is it useful?
+
+:::
+
+::::::::::::::::::::::::::::::::::::: keypoints 
+
+- Use GitHub Actions to automate checking your code each time you push changes to the repository.
+
+::::::::::::::::::::::::::::::::::::::::::::::::
+
+