Try example from docs

https://docs.github.com/en/enterprise-cloud@latest/actions/learn-github-actions/expressions#example-returning-a-json-object

.github/workflows/checkbox-promote-beta-to-candidate.yml

@@ -29,6 +29,7 @@ jobs:
  id: set-matrix
  run: |
  echo "matrix=$(jq -cn --argjson matrix "$(cat matrix.json)" '{include: $matrix}' | jq -R)" >> $GITHUB_OUTPUT
+ echo "matrix={\"include\":[{\"project\":\"foo\",\"config\":\"Debug\"},{\"project\":\"bar\",\"config\":\"Release\"}]}" >> $GITHUB_OUTPUT
  checkbox-promotion-beta-to-candidate-test:
  needs: generate-matrix
  runs-on: [self-hosted, testflinger]
@@ -38,8 +39,8 @@ jobs:
  steps:
  - name: diagnostics
  run: |
- echo ${{ matrix.queue }}
- echo ${{ matrix.data_source }}
- echo ${{ matrix.checkbox_runtime }}
- echo ${{ matrix.checkbox_track }} 
- 
+ echo "Matrix - Project ${{ matrix.project }}, Config ${{ matrix.config }}"
+ #echo ${{ matrix.queue }}
+ #echo ${{ matrix.data_source }}
+ #echo ${{ matrix.checkbox_runtime }}
+  #echo ${{ matrix.checkbox_track }}