Trying to rewrite an ugly macro

Question

I'm new to lisp, and have been trying to learn Common Lisp by diving in and writing some code. I've read plenty of documentation on the subject, but it's taking a while to really sink in.

I have written a couple of macros (? and ??) for performing unit tests, but I'm having some difficulty. The code is at the end of the post, to avoid cluttering the actual question.

Here is an example of usage:

(?? (? "Arithmetic tests" (? "Addition" (= (+ 1 2) 3) (= (+ 1 2 3) 6) (= (+ -1 -3) -4))))

And an example of output:

[Arithmetic tests] [Addition] (PASS) '(= (+ 1 2) 3)' (PASS) '(= (+ 1 2 3) 6)' (PASS) '(= (+ -1 -3) -4)' Results: 3 tests passed, 0 tests failed

Now, the existing code works. Unfortunately, the (? ...) macro is ugly, verbose, resistant to change - and I'm pretty sure also badly structured. For example, do I really have to use a list to store pieces of output code and then emit the contents at the end?

I'd like to modify the macro to permit description strings (or symbols) to optionally follow each test, whereupon it would replace the test literal in the output, thus:

(?? (? "Arithmetic tests" (? "Addition" (= (+ 1 2) 3) "Adding 1 and 2 results in 3" (= (+ 1 2 3) 6) (= (+ -1 -3) -4))))

Output:

[Arithmetic tests] [Addition] (PASS) Adding 1 and 2 results in 3 (PASS) '(= (+ 1 2 3) 6)' (PASS) '(= (+ -1 -3) -4)'

But unfortunately I can't find a sensible place in the macro to insert this change. Depending on where I put it, I get errors like you're not inside a backquote expression, label is not defined or body-forms is not defined. I know what these errors mean, but I can't find a way to avoid them.

Also, I'll be wanting to handle exceptions in the test, and treat that as a failure. Currently, there is no exception handling code - the test result is merely tested against nil. Again, it is not clear how I should add this functionality.

I'm thinking that maybe this macro is over-complex, due to my inexperience in writing macros; and perhaps if I simplify it, modification will be easier. I don't really want to separate it out into several smaller macros without good reason; but maybe there's a terser way to write it?

Can anyone help me out here, please?

A complete code listing follows:

(defmacro with-gensyms ((&rest names) &body body) `(let ,(loop for n in names collect `(,n (gensym))) ,@body)) (defmacro while (condition &body body) `(loop while ,condition do (progn ,@body))) (defun flatten (L) "Converts a list to single level." (if (null L) nil (if (atom (first L)) (cons (first L) (flatten (rest L))) (append (flatten (first L)) (flatten (rest L)))))) (defun starts-with-p (str1 str2) "Determine whether `str1` starts with `str2`" (let ((p (search str2 str1))) (and p (= 0 p)))) (defmacro pop-first-char (string) `(with-gensyms (c) (if (> (length ,string) 0) (progn (setf c (schar ,string 0)) (if (> (length ,string) 1) (setf ,string (subseq ,string 1)) (setf ,string "")))) c)) (defmacro pop-chars (string count) `(with-gensyms (result) (setf result ()) (dotimes (index ,count) (push (pop-first-char ,string) result)) result)) (defun format-ansi-codes (text) (let ((result ())) (while (> (length text) 0) (cond ((starts-with-p text "\\e") (push (code-char #o33) result) (pop-chars text 2) ) ((starts-with-p text "\\r") (push (code-char 13) result) (pop-chars text 2) ) (t (push (pop-first-char text) result)) )) (setf result (nreverse result)) (coerce result 'string))) (defun kv-lookup (values key) "Like getf, but works with 'keys as well as :keys, in both the list and the supplied key" (setf key (if (typep key 'cons) (nth 1 key) key)) (while values (let ((k (pop values)) (v (pop values))) (setf k (if (typep k 'cons) (nth 1 k) k)) (if (eql (symbol-name key) (symbol-name k)) (return v))))) (defun make-ansi-escape (ansi-name) (let ((ansi-codes '( :normal "\\e[00m" :white "\\e[1;37m" :light-grey "\\e[0;37m" :dark-grey "\\e[1;30m" :red "\\e[0;31m" :light-red "\\e[1;31m" :green "\\e[0;32m" :blue "\\e[1;34m" :dark-blue "\\e[1;34m" :cyan "\\e[1;36m" :magenta "\\e[1;35m" :yellow "\\e[0;33m" :bg-dark-grey "\\e[100m" :bold "\\e[1m" :underline "\\e[4m" :start-of-line "\\r" :clear-line "\\e[2K" :move-up "\\e[1A"))) (format-ansi-codes (kv-lookup ansi-codes ansi-name)) )) (defun format-ansi-escaped-arg (out-stream arg) (cond ((typep arg 'symbol) (format out-stream "~a" (make-ansi-escape arg))) ((typep arg 'string) (format out-stream arg)) (t (format out-stream "~a" arg)) )) (defun format-ansi-escaped (out-stream &rest args) (while args (let ((arg (pop args))) (if (typep arg 'list) (let ((first-arg (eval (first arg)))) (format out-stream first-arg (second arg)) ) (format-ansi-escaped-arg out-stream arg) )) )) (defmacro while-pop ((var sequence &optional result-form) &rest forms) (with-gensyms (seq) `(let (,var) (progn (do () ((not ,sequence)) (setf ,var (pop ,sequence)) (progn ,@forms)) ,result-form)))) (defun report-start (form) (format t "( ) '~a'~%" form)) (defun report-result (result form) (format-ansi-escaped t "(" (if result :green :red) `("~:[FAIL~;PASS~]" ,result) :normal `(") '~a'~%" ,form)) result) (defmacro ? (name &body body-forms) "Run any number of test forms, optionally nested within further (?) calls, and print the results of each test" (with-gensyms (result indent indent-string) (if (not body-forms) :empty (progn (setf result () indent 0 indent-string " ") (cond ((typep (first body-forms) 'integer) (setf indent (pop body-forms)))) `(progn (format t "~v@{~A~:*~}" ,indent ,indent-string) (format-ansi-escaped t "[" :white ,name :normal "]~%") (with-gensyms (test-results) (setf test-results ()) ,(while-pop (body-form body-forms `(progn ,@(nreverse result))) (cond ( (EQL (first body-form) '?) (push `(progn (setf test-results (append test-results (? ',(nth 1 body-form) ,(1+ indent) ,@(nthcdr 2 body-form)))) (format t "~%") test-results ) result) ) (t (push `(progn (format t "~v@{~A~:*~}" ,(1+ indent) ,indent-string) (report-start ',body-form) (with-gensyms (result label) (setf result ,body-form) (format-ansi-escaped t :move-up :start-of-line :clear-line) (format t "~v@{~A~:*~}" ,(1+ indent) ,indent-string) (push (report-result result ',body-form) test-results) test-results )) result)))))))))) (defun ?? (&rest results) "Run any number of tests, and print a summary afterward" (setf results (flatten results)) (format-ansi-escaped t "~&" :white "Results: " :green `("~a test~:p passed" ,(count t results)) :normal ", " (if (find NIL results) :red :normal) `("~a test~:p failed" ,(count NIL results)) :yellow `("~[~:;, ~:*~a test~:p not run~]" ,(count :skip results)) :brown `("~[~:;, ~:*~a empty test group~:p skipped~]" ,(count :empty results)) :normal "~%"))

Consider using an already existing test library such as prove or lisp-unit2. — Inaimathi
– Inaimathi, Commented Sep 1, 2015 at 2:51
By the looks of it, yes, feel free to come ask on codereview.stackexchange.com — Kaz
– Kaz, Commented Sep 1, 2015 at 6:57
Take a look at Chapter 9 (Practical: Building a Unit Test Framework) of Peter Seibel's Practical Common Lisp (gigamonkeys.com/book) — Terje D.
– Terje D., Commented Sep 1, 2015 at 20:05
@TerjeD. I have already read that, thank you. It was, in fact, what prompted me to have a go at writing one. — Sod Almighty
– Sod Almighty, Commented Sep 2, 2015 at 0:29

Stanislav Kondratyev · Accepted Answer · 2015-09-02 20:18:01Z

For my part, the ? macro is rather technical and it's hard to follow the logic behind the formatting functions. So instead of tracking errors I'd like to suggest my own attempt, perhaps it'll be of use.

I think that actually your ?? doesn't want to evaluate anything, but rather to treat its body as individual tests or sections. If the body includes a list starting with ?, this list represents a section; other elements are test forms optionally followed by descriptions. So in my implementation ?? will be a macro, and ? will be just a symbol.

I start with wishful thinking. I suppose I can create individual tests using a function make-test-item and test sections using a function make-test-section (their implementation is unimportant for now), that I can display them using an auxiliary function display-test and compute results using the function results, which returns two values: the total number of tests and the number of passed ones. Then I'd like the code

(?? (? "Arithmetic tests" (? "Addition" (= (+ 1 2) 3) "Adding 1 and 2 results in 3" (= (+ 1 2 3) 6) (= (+ -1 -3) 4)) (? "Subtraction" (= (- 1 2) 1))) (= (sin 0) 0) "Sine of 0 equals 0")

to expand into something like

(let ((tests (list (make-test-section :header "Arithmetic tests" :items (list (make-test-section :header "Addition" :items (list (make-test-item :form '(= (+ 1 2) 3) :description "Adding 1 and 2 results in 3" :passp (= (+ 1 2) 3)) (make-test-item :form '(= (+ 1 2 3) 6) :passp (= (+ 1 2 3) 6)) (make-test-item :form '(= (+ -1 -3) 4) :passp (= (+ -1 -3) 4)))) (make-test-section :header "Subtraction" :items (list (make-test-item :form '(= (- 1 2) 1) :passp (= (- 1 2) 1)))))) (make-test-item :form '(= (sin 0) 0) :passp (= (sin 0) 0) :description "Sine of 0 equals 0")))) (loop for test in tests with total = 0 with passed = 0 do (display-test test 0 t) do (multiple-value-bind (ttl p) (results test) (incf total ttl) (incf passed p)) finally (display-result total passed t)))

Here a list of tests is created; then we traverse it printing each test (0 denotes the zero level of indentation and t is as in format) and keeping track of the results, finally displaying the total results. I don't think explicit eval is needed here.

It may not be the most exquisite piece of code ever, but it seems manageable. I supply missing definitions below, they are rather trivial (and can be improved) and have nothing to do with macros.

Now we pass on to the macros. Consider both pieces of code as data, then we want a list processing function which would turn the first one into the second. A few auxiliary functions would come in handy.

The major task is to parse the body of ?? and generate the list of test to go inside the let.

(defun test-item-form (form description) `(make-test-item :form ',form :description ,description :passp ,form)) (defun test-section-form (header items) `(make-test-section :header ,header :items (list ,@items))) (defun parse-test (forms) (let (new-forms) (loop (when (null forms) (return (nreverse new-forms))) (let ((f (pop forms))) (cond ((and (listp f) (eq (first f) '?)) (push (test-section-form (second f) (parse-test (nthcdr 2 f))) new-forms)) ((stringp (first forms)) (push (test-item-form f (pop forms)) new-forms)) (t (push (test-item-form f nil) new-forms)))))))

Here parse-test essentially absorbs the syntax of ??. Each iteration consumes one or two forms and collects corresponding make-... forms. The functions can be easily tested in REPL (and, of course, I did test them while writing).

Now the macro becomes quite simple:

(defmacro ?? (&body body) `(let ((tests (list ,@(parse-test body)))) (loop for test in tests with total = 0 with passed = 0 do (display-test test 0 t) do (multiple-value-bind (ttl p) (results test) (incf total ttl) (incf passed p)) finally (display-result total passed t))))

It captures a few symbols, both in the variable name space and in the function one (the expansion may contain make-test-item and make-test-section). A clean solution with gensyms would be cumbersome, so I'd suggest just moving all the definitions in a separate package and exporting only ?? and ?.

For completeness, here is an implementation of the test API. Actually, it's what I started coding with and proceeded until I made sure the big let-form works; then I passed on to the macro part. This implementation is fairly sloppy; in particular, it doesn't support terminal colours and display-test can't even output a section into a string.

(defstruct test-item form description passp) (defstruct test-section header items) (defun results (test) (etypecase test (test-item (if (test-item-passp test) (values 1 1) (values 1 0))) (test-section (let ((items-count 0) (passed-count 0)) (dolist (i (test-section-items test) (values items-count passed-count)) (multiple-value-bind (i p) (results i) (incf items-count i) (incf passed-count p))))))) (defparameter *test-indent* 2) (defun display-test-item (i level stream) (format stream "~V,0T~:[(FAIL)~;(PASS)~] ~:['~S'~;~:*~A~]~%" (* level *test-indent*) (test-item-passp i) (test-item-description i) (test-item-form i))) (defun display-test-section-header (s level stream) (format stream "~V,0T[~A]~%" (* level *test-indent*) (test-section-header s))) (defun display-test (test level stream) (etypecase test (test-item (display-test-item test level stream)) (test-section (display-test-section-header test level stream) (dolist (i (test-section-items test)) (display-test i (1+ level) stream))))) (defun display-result (total passed stream) (format stream "Results: ~D test~:P passed, ~D test~:P failed.~%" passed (- total passed)))

All the code is licenced under WTFPL.

Thanks for your very detailed answer. I'm having a little trouble understanding it though. I see no definition for the (results) function; and I'm a little uncertain how the test headers get printed correctly. Seems I'm a little out of my depth :(
I've found the (results) function now ;) ... however it will take me some time to fully understand all this. I'll bang my head against it for a while and see what happens.

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