Since the project I work on (https://spdk.io) largely produces a set of executables as output, it was most natural to write the tests in bash. There's one top level bash script that kicks off the full suite of tests and thousands and thousands of lines of tests all written as bash scripts stringing together calls to these executables.

One of these tests is to run shellcheck against all of the scripts in the repo. We don't allow any modifications to scripts without shellcheck giving them the green light now. The quality of our tests has increased dramatically since this was instituted - it's a really great tool.