chore: switch test runner to pytest

Author: rocky-d

.github/copilot-instructions.md

@@ -9,7 +9,7 @@
 - Package manager: [uv](https://github.com/astral-sh/uv) - always use `uv run` for development commands
 - Linter/Formatter: [ruff](https://github.com/astral-sh/ruff) - configured in pyproject.toml
 - Type checker: [ty](https://github.com/astral-sh/ty) - use `uv run ty check`
-- Test framework: unittest
+- Test framework: pytest
 - Build backend: uv_build
 
 ## Code Conventions

.github/workflows/test.yml

@@ -26,7 +26,7 @@ jobs:
         run: uv sync --dev
 
       - name: Run tests
-        run: uv run python -m unittest discover tests/
+        run: uv run pytest
 
   coverage:
     runs-on: ubuntu-latest
@@ -43,9 +43,7 @@ jobs:
 
       - name: Run tests with coverage
         run: |
-          uv run coverage run -m unittest discover tests/
-          uv run coverage report
-          uv run coverage xml
+          uv run pytest --cov --cov-branch --cov-report=term --cov-report=xml
 
       - name: Upload coverage to Codecov
         uses: codecov/codecov-action@v5

pyproject.toml

@@ -36,6 +36,8 @@ Documentation = "https://rocky-d.github.io/dttb/"
 [dependency-groups]
 dev = [
     "coverage>=7.6.1",
+    "pytest>=8.0.0",
+    "pytest-cov>=5.0.0",
     "python-dotenv>=1.0.1",
     "pyyaml>=6.0.3",
     "ruff>=0.15.0",