A steam locomotive from 1993 broke my yarn test

Summary

So the story begins with a pair programming session I had with my colleague, which I desperately needed because my node skill tree is still at level 1, and I needed to get started with React because I'll be working on our internal backstage instance.We worked together on a small feature, tested it locally, and it worked. Great. Now it's time to make My Very First React Commit. So I ran the usual git add and git commit, which hooked into yarn test, to automatically run unit tests for backstage, and that's when everything got derailed. For all the React tutorials I have followed, I have never actually run a yarn test on my machine. And the first time I tried yarn test, it hung, and after a long time, the command eventually failed: Determining test suites to run... ● Test suite failed to run thrown: [Error] error Command failed with exit code 1. info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command. 🌈 backstage ⚡ I could tell it was obviously unhappy about something, and then it threw some [Error]. I have very little actual JavaScript experience, but this looks suspiciously like someone had neglected to write a proper toString() or whatever, and thus we're stuck with the monumentally unhelpful [Error]. Searching the web yielded an entire ocean of false positives due to how vague the error message is. What a train wreck!Fine, let's put on our troubleshooting hats. My memory is not perfect, but thankfully shell history is. Let's see all the (ultimately useless) things that were tried (with commentary): 2025-03-19 14:18 yarn test --help 2025-03-19 14:20 yarn test --verbose 2025-03-19 14:21 git diff --staged 2025-03-19 14:25 vim README.md # Did I miss some setup? 2025-03-19 14:28 i3lock -c 336699 # "I need a drink" 2025-03-19 14:34 yarn test --debug # Debug, verbose, what's the diff 2025-03-19 14:35 yarn backstage-cli repo test # Maybe if I invoke it directly ... 2025-03-19 14:36 yarn backstage-cli --version # Nope, same as mengnan's 2025-03-1...