Manuel Klimek

Some time ago a a discussion in the testdrivendevelopment Yahoo-Group evolved around the concept of "testable languages". I thought about this for a while and came up with the idea that I want to be able to have expressions as first class citizens:

assertThat { assertThat(false) } abortsWith TestFailedException

Today I played a little with OCaml, sorted my functional programming skillz out, and finally arrived at my first test driven unit test environment for OCaml! Note that it's nearly what I wanted to be able to write, but unfortunately there's not enough syntactic sugar for lambda expressions (or I didn't find out, yet), so I'm stuck with using the quite ugly ( function () -> expression ) syntax. But hey, it's really close to heaven.

exception TestFailed
exception TestError

let failsWith expectedError expression =
	try
		expression ();
		false
	with error ->
		expectedError = error

let isTrue expression: bool =
	expression

let isFalse expression: bool =
	not (expression)

let assertThat expression conditionMatchesOn =
	if not (conditionMatchesOn (expression)) then
		raise TestFailed
	else
		()

let _ = (
	assertThat true isTrue;
	assertThat (isTrue true) isTrue;
	assertThat (not (isTrue false)) isTrue;

	assertThat false isFalse;
	assertThat (isFalse false) isTrue;

	assertThat (TestFailed = TestFailed) isTrue;
	assertThat (failsWith TestError (function () -> raise TestError)) isTrue;
	assertThat (failsWith TestFailed (function () -> raise TestError)) isFalse;
	assertThat
		( function () -> assertThat false isTrue )
		( failsWith TestFailed );

	Printf.printf "OK\n";
);;