Expect is an automation framework. Automating tests is just one use for it.

Expect was born out of TCL, and its original syntax worked really well with TCL's.

Its popularity led it to being ported to other languages, Perl & Python being the big ones, but TCL Expect is the og

SQLite has the same origin story. (That's the reason for SQLite's confusing type system: it makes perfect sense as a Tcl type system.)