Add codecov

Author: mjwen

.github/workflows/testing.yml

@@ -73,4 +73,10 @@ jobs:
       - name: Test with pytest
         run: |
           cd tests
-          pytest
+          pytest --cov=kliff --cov-report=xml
+
+      - uses: codecov/codecov-action@v4
+        if: matrix.os == 'ubuntu-latest' && matrix.python-version == '3.10' && github.repository == 'openkim/kliff'
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          file: ./coverage.xml

setup.py

@@ -117,6 +117,7 @@ def get_readme():
     extras_require={
         "test": [
             "pytest",
+            "pytest-cov",
             "kimpy",
             "emcee",
             "ptemcee @ git+https://github.com/yonatank93/ptemcee.git@enhance_v1.0.0",