How to debug tests (Github Actions)

You need an SSH-key registered with GitHub. You either pick the key you have already used with github.com or you create a dedicated new one with ssh-keygen -t ed25519 -a 64 -f tmate_ed25519 -C "$(date +'%d-%m-%Y')" and add it at https://github.com/settings/keys.
Add the following snippet to ~/.ssh/config:

Host *.tmate.io
    User git
    AddKeysToAgent yes
    UseKeychain yes
    PreferredAuthentications publickey
    IdentitiesOnly yes
    IdentityFile ~/.ssh/tmate_ed25519

Go to https://github.com/<user>/<repo>/actions/workflows/tests.yml.
Click the Run workflow button and you will have the option to select the branch to run the workflow from and activate tmate by checking the Debug with tmate checkbox for this run.

After the workflow_dispatch event was triggered, click the All workflows link in the sidebar and then click the tests action in progress workflow.
Pick one of the jobs in progress in the sidebar.
Wait until the current task list reaches the tmate debugging session section and the output shows something like:

106 SSH: ssh [email protected]
107 or: ssh -i <path-to-private-SSH-key> [email protected]
108 SSH: ssh [email protected]
109 or: ssh -i <path-to-private-SSH-key> [email protected]

Copy and execute the first option ssh [email protected] in the terminal and continue by pressing either q or Ctrl + c.
Start the Bats test with bats ./tests/test.bats.

For a more detailed documentation about tmate see Debug your GitHub Actions by using tmate.