In 2011 I created Bats, a test harness for bash, which went on to have a life of its own: https://github.com/bats-core/bats-core
Now I’m working on a 2026 take on the problem, this time targeting POSIX shell. It’s called Brat (the Brutal Runner for Automated Tests).
Here’s a video showing Brat running its own test suite, first serially, and again using 8 parallel jobs: