test: add macos and windows to CI matrix

.github/workflows/ci.yml

@@ -14,9 +14,10 @@ jobs:
   test:
     strategy:
       matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
         pixi-version: ["0.18.0"]
         python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
-    runs-on: ubuntu-22.04
+    runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout repo
         uses: actions/checkout@v4
@@ -35,11 +36,11 @@ jobs:
       - name: Install environment
         run: poetry install
       - name: Test with nox
-        run: poetry run nox -s test-${{ matrix.python-version }} integration-${{ matrix.python-version }} 
+        run: poetry run nox -s test-${{ matrix.python-version }} integration-${{ matrix.python-version }}
       - name: Store coverage
         uses: actions/upload-artifact@v4
         with:
-          name: coverage-${{ matrix.python-version }}
+          name: coverage-${{ matrix.python-version }}-${{ matrix.os }}
           path: .coverage.*
   coverage:
     needs: test

noxfile.py

@@ -1,3 +1,4 @@
+import platform
 from typing import List
 
 from nox import options, parametrize
@@ -9,14 +10,14 @@
 @session(python=["3.8", "3.9", "3.10", "3.11", "3.12"])
 def test(s: Session):
     s.install(".", "pytest", "pytest-cov")
-    s.env["COVERAGE_FILE"] = f".coverage.{s.python}"
+    s.env["COVERAGE_FILE"] = f".coverage.{s.python}.{platform.system()}"
     s.run("python", "-m", "pytest", "--cov", "pixi_kernel")
 
 
 @session(python=["3.8", "3.9", "3.10", "3.11", "3.12"])
 def integration(s: Session):
     with s.chdir("tests/integration"):
-        s.run("pixi", "run", "python", "kernel.py")
+        s.run("pixi", "run", "python", "kernel.py", external=True)
 
 
 @session(venv_backend="none")