Function assert

test/fixtures/wpt/resources/testharness.js:4774–4781

(expected_true, function_name, description, error, substitutions)

     * Utility functions
     */
    function assert(expected_true, function_name, description, error, substitutions)
    {
        if (expected_true !== true) {
            var msg = make_message(function_name, description,
                                   error, substitutions);
            throw new AssertionError(msg);
        }
    }

    /**
     * @class