ci: GitHub Actions workflow + base pipeline unit tests

.github/workflows/ci.yml

@@ -0,0 +1,85 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    name: Tests (Python 3.13)
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Python 3.13
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.13"
+          cache: pip
+          cache-dependency-path: |
+            requirements.txt
+            pyproject.toml
+
+      - name: Upgrade pip and install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          # Install runtime deps (skip iqm-client which is hardware-only and not needed for tests)
+          pip install -r requirements.txt
+          # Install test dependencies
+          pip install pytest>=8.0 pytest-cov>=5.0
+
+      - name: Run tests with coverage
+        run: |
+          pytest \
+            --cov=. \
+            --cov-report=term-missing \
+            --cov-report=xml \
+            --cov-report=html \
+            --cov-fail-under=85 \
+            -v \
+            tests/
+
+      - name: Upload coverage to Codecov (optional)
+        if: success()
+        uses: codecov/codecov-action@v4
+        with:
+          files: ./coverage.xml
+          fail_ci_if_error: false
+          token: ${{ secrets.CODECOV_TOKEN }}
+          continue-on-error: true
+
+  smoke:
+    name: DiffQEC smoke test
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    needs: test
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Python 3.13
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.13"
+          cache: pip
+          cache-dependency-path: |
+            requirements.txt
+            pyproject.toml
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r requirements.txt
+
+      - name: Run DiffQEC smoke test
+        run: |
+          python -m diffqec.smoke_test

conftest.py

@@ -0,0 +1,13 @@
+"""Pytest configuration: add the project root to sys.path.
+
+This lets test files import from the project modules (surface_code,
+extract_syndromes, internal_helpers, etc.) without requiring the project
+to be installed as a package.
+"""
+import sys
+from pathlib import Path
+
+# Add the project root to sys.path so tests can import project modules
+_PROJECT_ROOT = Path(__file__).resolve().parent
+if str(_PROJECT_ROOT) not in sys.path:
+    sys.path.insert(0, str(_PROJECT_ROOT))

pytest.ini

@@ -0,0 +1,44 @@
+[pytest]
+testpaths = tests
+python_files = test_*.py
+python_classes = Test*
+python_functions = test_*
+pythonpath = .
+addopts =
+    -ra
+    --strict-markers
+    --tb=short
+    --disable-warnings
+markers =
+    slow: marks tests as slow (deselect with -m 'not slow')
+    hardware: marks tests that require real quantum hardware (skipped in CI)
+filterwarnings =
+    ignore::DeprecationWarning:qiskit.*
+    ignore::DeprecationWarning:stim.*
+    ignore::DeprecationWarning:pymatching.*
+
+[coverage:run]
+source =
+    surface_code
+    extract_syndromes
+    internal_helpers
+    run_on_hardware
+    diffqec
+omit =
+    tests/*
+    iqm_utils/*
+    benchmarks/*
+    lumi/*
+    main.py
+    build_emerald_qubit_rotated.py
+
+[coverage:report]
+exclude_lines =
+    pragma: no cover
+    raise NotImplementedError
+    if __name__ == .__main__.:
+    def __repr__
+    \.\.\.
+precision = 1
+show_missing = true
+skip_covered = false

requirements.txt

@@ -17,4 +17,7 @@ iqm-client==34.0.3
 
 # --- DiffQEC decoder (discrete diffusion model) ---
 torch>=2.0
-
+
+# --- Test dependencies (CI) ---
+pytest>=8.0
+pytest-cov>=5.0