ci: migrate to matrix

Author: felbinger

.github/workflows/ci.yaml

@@ -73,4 +73,39 @@ jobs:
         uses: cachix/install-nix-action@7ec16f2c061ab07b235a7245e06ed46fe9a1cab6 # v31.8.3
 
       - name: Check flake
-        run: nix -L flake check
+        run: nix -L flake check --no-build
+
+  list-tests:
+    name: list nix checks
+    runs-on: ubuntu-24.04
+    outputs:
+      matrix: ${{ steps.generate-matrix.outputs.matrix }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5
+
+      - name: Install Nix
+        uses: cachix/install-nix-action@7ec16f2c061ab07b235a7245e06ed46fe9a1cab6 # v31.8.3
+
+      - name: Generate test matrix
+        id: generate-matrix
+        run: |
+          matrix=$(nix flake show --json | jq -r '.checks["x86_64-linux"] | keys | tojson')
+          echo "matrix=${matrix}" >> $GITHUB_OUTPUT
+
+  test:
+    name: "nix build .#checks.x86_64-linux.${{ matrix.name }}"
+    needs: [ list-tests, eval ]
+    strategy:
+      matrix:
+        name: ${{ fromJson(needs.list-tests.outputs.matrix) }}
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5
+
+      - name: Install Nix
+        uses: cachix/install-nix-action@7ec16f2c061ab07b235a7245e06ed46fe9a1cab6 # v31.8.3
+
+      - name: Run integration test
+        run: nix -L build .#checks.x86_64-linux.${{ matrix.name }}