There are many black box modules in the tests, which have the (* whitebox *) attribute. For example:

/*
 * `input wire a` should be detected as a clock because of the `(* CLOCK *)`
 * attribute.
 */
(* whitebox *)
module BLOCK(a, b, o);
	(* CLOCK *)
	input wire a;
	input wire b;
	output wire o;
endmodule

I think the documentation should give a brief explanation on why there is a (* whitebox *) attribute, what is the reason to put this there. Perhaps this could be done on it's own page so that we don't repeat it everywhere (in a separate issue/PR).

(Actually, I myself don't know why is that attribute included.)

Originally posted by @daniellimws in #42 (comment)