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OUnit - xUnit testing framework for OCaml

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OUnit is a unit test framework for OCaml. It allows one to easily create unit-tests for OCaml code. It is loosely based on HUnit, a unit testing framework for Haskell. It is similar to JUnit, and other XUnit testing frameworks.


  • colored output
  • JUnit report generation
  • HTML report generation


The recommended way to install ounit is via the opam package manager:

$ opam install ounit2


API documentation is available online.


Transition to ounit2

In the past OUnit used the ocamlfind package name "oUnit". It is uncommon to use uppercase letters in ocamlfind package name. It caused some problems during the transition to "dune". It was also not the same name as the OPAM package. As of version 2.2, the opam package ounit and the ocamlfind package oUnit are renamed to ounit2 (the same for both the ocamlfind and opam packages).

To do the transition for your own tests:

  • in OPAM, the library should now depends on "ounit2" or "ounit2-lwt"
  • in dune files/OASIS/Makefile/ replace "oUnit" by "ounit2" and "ounit-lwt" to "ounit2-lwt".

We will keep OPAM packages "ounit"/"ounit-lwt" for the transition.