testing.yml

---
name: testing

"on":
  pull_request:
  push:
    branches:
      - master

jobs:
  rubocop:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout source
        uses: actions/checkout@v4

      - name: Setup ruby
        uses: ruby/setup-ruby@v1
        with:
          ruby-version: 2.1
          bundler: 1.17
          bundler-cache: true

      - name: Run rubocop
        run: bundle exec rubocop

  spec:
    runs-on: ubuntu-latest
    needs: rubocop

    strategy:
      fail-fast: false

      matrix:
        ruby:
          - "2.1"
          - "2.5"
          - "2.7"
          - "3.0"
          - "3.1"
        json:
          - "1.6"
          - "1.7"
          - "1.8"
          - "2.0"
          - "2.1"
          - "2.2"
          - "2.3"
          - "2.4"
          - "2.5"
          - "2.6"
        exclude:
          - json: "2.6"
            ruby: "2.1"
          - json: "2.7"
            ruby: "2.3"

    steps:
      - name: Checkout source
        uses: actions/checkout@v4

      - name: Setup ruby
        uses: ruby/setup-ruby@v1
        with:
          ruby-version: ${{ matrix.ruby }}
          bundler: 1.17
          bundler-cache: true
        env:
          JSON_VERSION: ${{ matrix.json }}

      - name: Run rspec
        run: bundle exec rspec

...