Test that image layers and compose volumes are getting cached

https://ampcode.com/threads/T-019b9de3-53bf-72ff-970b-6e25b1db5b09

Author: dzhlobo

.github/workflows/ci.yml

@@ -6,7 +6,7 @@ on:
     branches: [main]
 
 jobs:
-  verify-dist:
+  setup-and-cache:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -17,11 +17,30 @@ jobs:
           volumes: |
             node_modules: ${{ hashFiles('package-lock.json') }}
       - run: bin/setup
-      - run: bin/npm run build
-      - name: Check for uncommitted changes
+
+  test:
+    needs: setup-and-cache
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: docker/setup-buildx-action@v3
+      - uses: docker/setup-compose-action@v1
+      - uses: ./
+        with:
+          volumes: |
+            node_modules: ${{ hashFiles('package-lock.json') }}
+      - name: Verify caches are used
         run: |
-          if [ -n "$(git status --porcelain dist/)" ]; then
-            echo "::error::dist/ is out of date. Run 'npm run build' and commit the changes."
-            git diff dist/
+          output=$(bin/setup 2>&1)
+          echo "$output"
+          # Check that all build steps (except FROM) have a CACHED line
+          for step in $(echo "$output" | grep -oE '^#[0-9]+ \[[0-9]+/[0-9]+\]' | grep -v FROM | grep -oE '^#[0-9]+'); do
+            if ! echo "$output" | grep -q "^${step} CACHED"; then
+              echo "::error::Step $step was rebuilt instead of using cache"
+              exit 1
+            fi
+          done
+          if echo "$output" | grep -q "added"; then
+            echo "::error::Packages were downloaded instead of using cached node_modules"
             exit 1
           fi