group-bug:
  runs-on: windows-latest
  steps:

  - run: |
           :
           echo ---
           echo Warning single
           echo Error single
           echo [Warning] single
           echo [Error] single
           echo ---
           echo ::group::Warning grouped
           echo grouped
           echo warnings
           echo ::endgroup::
           echo ---
           echo ::group::Error grouped
           echo grouped
           echo errors
           echo ::endgroup::
           echo ---
           echo ::group::[Warning] grouped
           echo grouped
           echo warnings
           echo ::endgroup::
           echo ---
           echo ::group::[Error] grouped
           echo grouped
           echo errors
           echo ::endgroup::
           echo ---
    shell: bash