Add code coverage tests

.github/workflows/testing.yml

@@ -114,7 +114,6 @@ jobs:
       - name: Install dependencies
         run: |
           uv sync --all-extras
-          uv pip install pytest-cov
 
       - name: Download spaCy models
         run: |
@@ -130,5 +129,28 @@ jobs:
           uv run python -m nltk.downloader words
 
       - name: Run tests with coverage
+        # --cov-fail-under enforces the overall regression floor (configured in
+        # pyproject.toml [tool.coverage.report] fail_under = 33).
+        # Patch coverage (new/changed lines ≥ 80%) is enforced by Codecov below.
         run: |
-          uv run pytest tests/ --cov=src/risk_assessment --cov-report=xml --cov-report=html --cov-report=term
+          uv run pytest tests/ \
+            --cov=src/risk_assessment \
+            --cov-report=xml \
+            --cov-report=html \
+            --cov-report=term-missing
+
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v5
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          files: coverage.xml
+          fail_ci_if_error: true
+          verbose: true
+
+      - name: Upload HTML coverage report as artifact
+        uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: coverage-html-report
+          path: htmlcov/
+          retention-days: 14

codecov.yml

@@ -0,0 +1,23 @@
+coverage:
+  status:
+    project:
+      # Overall coverage must not drop below the current baseline.
+      # `target: auto` means "don't regress from the last commit on the base branch".
+      # The 1% threshold gives a small float to absorb measurement noise.
+      default:
+        target: auto
+        threshold: 1%
+        informational: false   # fails the PR check if breached
+
+    patch:
+      # Lines added or changed by the PR must be covered at ≥ 80%.
+      default:
+        target: 80%
+        threshold: 0%
+        informational: false   # fails the PR check if breached
+
+comment:
+  layout: "reach,diff,flags,files"
+  behavior: default            # updates the existing comment on re-push
+  require_changes: true        # only post when coverage actually changes
+  hide_project_coverage: false

pyproject.toml

@@ -165,4 +165,18 @@ include = ["src", "tests"]
 exclude = [".pre-commit-config.yaml"]
 
 [tool.pytest.ini_options]
-addopts = "--cov=risk_assessment --cov-report html"
+addopts = "--cov=src/risk_assessment --cov-report=html --cov-report=xml --cov-report=term-missing"
+
+[tool.coverage.run]
+source = ["src/risk_assessment"]
+omit = [
+    "*/tests/*",
+    "*/__init__.py",
+]
+
+[tool.coverage.report]
+# Regress guard: overall coverage must not drop below this.
+# Update this value when coverage genuinely improves.
+fail_under = 33
+show_missing = true
+skip_covered = false