Make stub code not hang indefinitely in tests

[NicMcPhee]

At the moment the initial stub code causes the bats tests to hang indefinitely. This causes GitHub actions to hang forever until GitHub kills the test (over 5 hours at the moment), and can create confusion for students.

[NicMcPhee]

@floogulinc pointed out that we can add timeouts to GitHub Actions, which would make sense here to help manage situations where students inadvertently create non-terminating systems. See https://help.github.com/en/github/automating-your-workflow-with-github-actions/workflow-syntax-for-github-actions#jobsjob_idtimeout-minutes for info on how to do this.