Simple function for testing Standard ML code

tests.sml

use "hw2.sml";

fun test (tests) = 
    let 
        fun assess ([], _) = []
          | assess (x::rest, num) = if x then assess(rest,num+1) 
                                    else Int.toString(num)^""::assess(rest,num+1)
        val results = assess(tests,1)
    in
    case results of [] => "OK"
                  | _ => "FAILURES: " ^ String.concatWith", " results
    end

val task_1a = test [
        all_except_option("foo", []) = NONE,
        all_except_option("foo", ["foo","bar"]) = SOME ["bar"],
        all_except_option("bar", ["foo","bar"]) = SOME ["foo"],
        all_except_option("bar", ["foo","bar", "baz"]) = SOME ["foo","baz"],
        all_except_option("xxx", ["foo","bar"]) = NONE,
        all_except_option("foo", ["foo"]) = SOME []
    ]

(* etc *)