The Broken project aims at delivering an easy-to use testing framework for OCaml.

This shows how to create a testsuite example containing two test cases opposite and not_found testing for some computation returning the value 0 and some other to raise the Not_found exception:

register_suite "example" "Example of unit tests" [

  assert_zero "opposite"
    (fun (a,b) -> a - b) (1,1);

  assert_exception "not_found"
    Not_found (fun x -> List.mem x []) 0;
]

This is a more advanced example, illustrating the use of a custom test-case function assert_maybe_string, which is specialised in the production of test-cases for computations yielding string options, that is, computations in the so called maybe string monad.

register_suite "maybe" "Test the maybe monad" [

  assert_maybe_string "map"
    (Maybe.map String.uppercase) (Some "a") (Some "A");

  assert_maybe_string "map_infix"
    (Maybe.Infix.( <$> ) String.uppercase) (Some "a") (Some "A");

  assert_maybe_string "apply"
    (Maybe.apply (Some(String.uppercase))) (Some "a") (Some "A");

  assert_maybe_string "apply_infix"
    (Maybe.Infix.( <*> ) (Some(String.uppercase))) (Some "a") (Some "A");

  assert_maybe_string "apply_left_1"
    (Maybe.Infix.( <* ) None) (Some "b") None;

  assert_maybe_string "apply_left_2"
    (Maybe.Infix.( <* ) (Some "a")) (Some "b") (Some "a");

  assert_maybe_string "apply_right_1"
    (Maybe.Infix.( >* ) None) (Some "b") None;

  assert_maybe_string "apply_right_2"
    (Maybe.Infix.( >* ) (Some "a")) (Some "b") (Some "b");
];

The custom function assert_maybe_string is defined by

let assert_maybe_string id ?expected_failure f a b =
  assert_equal
    id
    ?expected_failure
    ~printer:(Maybe.format Format.pp_print_string)
    ~equal:( (=) )
    f a b

The full example can be found as part of the Mixture library.

The function Broken.main is the entry point of the unit-testing program running our test cases. It supports a few options, use the -h option on the command line for a short help:

Usage: unit-testing [-h | -l | -x | suite1 [suite2 [...]]]
 Run unitary tests
Options:
 -h Display a cheerful help message.
 -l List available test suites.
 -x List all test suites marked as expected failures.
Exit Status:
 The unit-testing program exits 0 on success and 1 if a test case
 failed.

Each registered test suite produces a test journal while being run. The test journal is in a format reminescent of the UNIX mailbox format, where each test case writes a message, whose body is the output of the test case and the headers indicate status of the execution. The assert_equal function uses its printer to write in the journal any difference between the value it expects from a computation and the value it actually recieves from it. Here is an example of the header of a failed test:

From BROKEN Thu Aug 13 10:06:14 2015
Test-Case: monad.list.cartesian_product
Test-Expected: [(1, 4); (1, 5); (2, 4); (2, 5); (3, 4); (3, 5)]
Test-Got: [(1, 4); (2, 4); (3, 4); (1, 5); (2, 5); (3, 5)]
Test-Outcome-Brief: ~
Test-Outcome: failed

Note that the test case is identified with a dotted path, which reads as “the test case cartesian_product in the test suite list in the test suite monad”, which makes it easy to find the test case definition in case of failure. Complex test cases will likely print additional output on stdout which is diverted to the body of the test journal message.

It is written by Michael Grünewald and is distributed as a free software: copying it and redistributing it is very much welcome under conditions of the CeCILL-B licence agreement, found in the COPYING and COPYING-FR files of the distribution.

It is easy to install Broken using opam and its pinning feature. In a shell visiting the repository, say

% autoconf
% opam pin add broken .

It is also possible to install Broken manually. The installation procedure is based on the portable build system BSD Owl Scripts written for BSD Make.

1. Verify that prerequisites are installed:

   • BSD Make
   • BSD OWl
   • OCaml
   • GNU Autoconf

2. Get the source, either by cloning the repository or by exploding a distribution tarball.

3. Optionally run autoconf to produce a configuration script. This is only required if the script is not already present.

4. Run ./configure, you can choose the installation prefix with --prefix.

5. Run make build.

6. Optionally run make test to test your build.

7. Finally run make install.

Depending on how BSD Make is called on your system, you may need to replace make by bsdmake or bmake in steps 5, 6, and 7. The GNU Make program usually give up the ghost, croaking *** missing separator. Stop. when you mistakingly use it instead of BSD Make.

Step 7 requires that you can su - if you are not already root.

Michael Grünewald in Berlin, on June 28, 2015