How to auto balance CI build with RSpec in Queue Mode and yarn tests executed only on first CI node

circle.yml

test:
  override:
    # run yarn tests only on first CI node
    # note we will do yarn install on first CI node so other CI nodes can run rspec tests in the mean time
    - case $CIRCLE_NODE_INDEX in 0) bundle exec yarn install; yarn flow -- check; yarn test -- --runInBand ;; esac:
        parallel: true # Caution: there are 8 spaces indentation!

    # Step for Dynamic RSpec allocation
    # It will auto balance the whole build
    - bundle exec rake knapsack_pro:queue:rspec:
        parallel: true # Caution: there are 8 spaces indentation!