Add code coverage calculation (jazzband#547)

* Add code coverage calculation

- Add code coverage
- Add upload to codecov
- Add badge to readme

Author: dancergraham

.github/workflows/python-package.yml

@@ -125,13 +125,42 @@ jobs:
         run: |
           sphinx-build -b html docs docs/_build
 
+  coverage:
+    runs-on: ubuntu-latest
+    needs: test
+
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Python 3.13
+        uses: actions/setup-python@v5
+        with:
+          python-version: 3.13
+      - name: Install dependencies
+        run: |
+          python -m venv .venv
+          source .venv/bin/activate
+          python -m pip install --upgrade pip
+          python -m pip install -r requirements.txt
+          python -m pip install coverage
+      - name: Run coverage
+        run: |
+          source .venv/bin/activate
+          export DJANGO_SETTINGS_MODULE="test_settings"
+          export PYTHONPATH=.".:$PYTHONPATH"
+          python -m coverage run --source=waffle `which django-admin` test waffle
+          coverage report -m
+          coverage html
+          coverage xml
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v5
+
   release-production:
     # Only upload if a tag is pushed (otherwise just build & check)
     if: github.event_name == 'push' && startsWith(github.event.ref, 'refs/tags')
 
     runs-on: ubuntu-latest
 
-    needs: [test, lint, i18n, docs]
+    needs: [test, lint, i18n, docs, coverage]
 
     steps:
       - uses: actions/checkout@v4

README.rst

@@ -18,7 +18,9 @@ a number of ways.
 .. image:: https://img.shields.io/readthedocs/waffle
    :target: https://app.readthedocs.org/projects/waffle
    :alt: Read the Docs
-
+.. image:: https://codecov.io/gh/jazzband/django-waffle/branch/master/graph/badge.svg
+   :target: https://codecov.io/gh/jazzband/django-waffle
+   :alt: Codecov
 
 :Code:          https://github.com/jazzband/django-waffle
 :License:       BSD; see LICENSE file

requirements/test.txt

@@ -1,2 +1,3 @@
 ruff
 tox
+coverage