libounit-ocaml-dev binary package in Ubuntu Bionic arm64

 OUnit is a unit testing framework for OCaml, imspired
 by the JUnit tool for Java and the HUnit tool for Haskell.
 .
 OUnit is designed to provide a convenient way for you to write tests
 for your OCaml code. Tests can be aggregated into test suites, making
 it easy to both write tests close to the code being examined and
 execute a comprehensive aggregate set of tests -- or any subset of it.

Source package