08 Bisect

Sometimes, the programming lanugage itself can help you with glass box testing. Often, languages provide support to determine if you've excercised every branch. OCaml's support for this comes in a tool called Bisect. Let's do this with our leap_year function from before.

let leap_year y = 
	y mod 4 = 0
	&& (y mod 100 <> 0 || y mod 400 = 0)

val leap_year : int -> bool = <fun>

Now let's write some unit tests. First a helper function:

#require "ounit2"
open OUnit2

let leap_year_test (n, y, b) =
	n >:: fun _ -> assert_equal b (leap_year y)

/Users/williambarkoff/.opam/cs3110-2021sp/lib/bytes: added to search path
/Users/williambarkoff/.opam/cs3110-2021sp/lib/stdlib-shims: added to search path
/Users/williambarkoff/.opam/cs3110-2021sp/lib/stdlib-shims/stdlib_shims.cma: loaded
/Users/williambarkoff/.opam/cs3110-2021sp/lib/ocaml/unix.cma: loaded
/Users/williambarkoff/.opam/cs3110-2021sp/lib/ounit2/advanced: added to search path
/Users/williambarkoff/.opam/cs3110-2021sp/lib/ounit2/advanced/oUnitAdvanced.cma: loaded
/Users/williambarkoff/.opam/cs3110-2021sp/lib/ounit2: added to search path
/Users/williambarkoff/.opam/cs3110-2021sp/lib/ounit2/oUnit.cma: loaded

val leap_year_test : string * int * bool -> OUnit2.test = <fun>

let tests = List.map leap_year_test  [
	"non leap year", 2010, false;
	(* we'll add some more tests later. *)
]

let suite = "Leap year" >::: tests

val tests : OUnit2.test list =
  [OUnitTest.TestLabel ("non leap year",
    OUnitTest.TestCase (OUnitTest.Short, <fun>))]

val suite : OUnit2.test =
  OUnitTest.TestLabel ("Leap year",
   OUnitTest.TestList
    [OUnitTest.TestLabel ("non leap year",
      OUnitTest.TestCase (OUnitTest.Short, <fun>))])

Now let's run our test suite

(jupyter doesn't like this)

.
Ran: 1 tests in 0.00 seconds.
OK

OK my jupyter notebook doesn't like any of this...

Basically, there's a tool called bisect. It is a coverage tool, tells you which branches you've hit and which you've haven't. Read the textbook chapter 7.4 is the bottom line here.