Develop a unit testing system

[gfngfn]

Config files:

 language: "0.1.0"
 contents:
   type: "library"
   …
+  test_directories:
+  - "./test"

(Black-box) tests:

module CalcTest = struct

  #[test]
  val add_test =
    let expected = 99 in
    let got = Calc.add 42 57 in
    if got == expected then
      ()
    else
      abort-with-message (`expected: `# ^ (arabic expected) ^ `, got: `# ^ (arabic got))

end

How to run tests:

$ satysfi test dir/of/your-package