Enable code coverage with Codecov

.github/codecov.yml

@@ -0,0 +1,18 @@
+# Configuration for Codecov: https://docs.codecov.com/docs/codecov-yaml
+#
+# Coverage reports are generated by `nox -s coverage-<python>` and
+# uploaded in .github/workflows/ci.yml.
+
+coverage:
+  status:
+    project:
+      default:
+        informational: true  # report coverage without failing checks
+    patch:
+      default:
+        informational: true
+
+comment:
+  layout: diff, flags, files
+  behavior: default
+  require_changes: true

.github/workflows/ci.yml

@@ -55,10 +55,10 @@ jobs:
           python: '3.13'
           nox_session: tests-3.13
 
-        - name: Tests, Python 3.12
+        - name: Tests with code coverage, Python 3.12
           os: ubuntu-latest
           python: '3.12'
-          nox_session: tests-3.12
+          nox_session: coverage-3.12
 
         - name: Tests, Python 3.11
           os: macos-latest

noxfile.py

@@ -65,6 +65,26 @@ def tests(session: nox.Session) -> None:
     session.run("pytest", *doctest_options, *session.posargs)
 
 
+@nox_uv.session(uv_groups=["test"], python=SUPPORTED_PYTHON_VERSIONS)
+def coverage(session: nox.Session) -> None:
+    """
+    Run tests with pytest and measure code coverage.
+
+    The project is installed in editable mode (by ``uv sync``) so that
+    file paths in the coverage report point to ``src/``, which is
+    needed for the report uploaded to Codecov to map onto the source.
+
+    Configuration: ``[tool.coverage]`` in pyproject.toml
+    """
+    session.run(
+        "pytest",
+        "--cov",
+        "--cov-report=xml",
+        "--cov-report=term",
+        *session.posargs,
+    )
+
+
 if RUNNING_ON_RTD:
     rtd_output_path = pathlib.Path(os.environ.get("READTHEDOCS_OUTPUT")) / "html"  # ty: ignore[invalid-argument-type]
     rtd_output_path.mkdir(parents=True, exist_ok=True)

pyproject.toml

@@ -1,3 +1,3 @@
 [build-system]
 build-backend = "uv_build"
 requires = [ "uv-build>=0.12.5,<0.13" ]
@@ -50,6 +50,7 @@
   "cdflib",
   "pytest",
   "pytest-check>=2.9.1",
+  "pytest-cov",
   "pytest-filter-subpackage",
   "xarray>=2022.6,<2023.10; python_version<'3.11'",
   "xarray>=2024.6; python_version>='3.11'",
@@ -284,3 +285,15 @@
 ]
 strict = true
 testpaths = [ "tests", "src/pyfaradaycup" ]
+
+[tool.coverage]  # https://coverage.readthedocs.io/en/latest/config.html
+run.source_pkgs = [ "pyfaradaycup" ]
+run.branch = true
+paths.source = [ "src/pyfaradaycup", "*/site-packages/pyfaradaycup" ]
+report.exclude_also = [
+  "@overload",
+  "if __name__ == .__main__.:",
+  "if TYPE_CHECKING:",
+  "raise NotImplementedError",
+]
+report.show_missing = true