TDD system for Common Lisp

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Colin OKeefe <colin@cicadas.surf>


A testiere is armor for the head of a horse and testiere is armor

for the your lisp forms.


With testiere, you embed test expressions directly into your code. When you compile, those tests are run. If any tests fail, you are dropped into the debugger where you can decide what to do.

This approach has several beneifts:

  1. *Does Not Add Dependencies* You do not need to add testiere asa dependency to your project. It is enough to load testiere intoyour Lisp image and evoke (testiere:on).
  2. *TDD* Common Lisp is a language well suited to interactivedevelopment. Why should testing be any different? With testiereyou can test functions as you C-c C-c them in SLIME, or wheneveryou load or compile a file.
  3. *Self Documentation* Because tests are in the source (but do notend up compiled into executable code unless testiere is "on"),you get purposeful documentation of your code for free. Why read acomment when there's a test!?

Out of the box, testiere supports testing of the following:

  • defun
  • defmethod
  • deftype
  • defclass
  • defstruct

1.1A Basic Example

(defun add3 (x y z)
  "Adds three numbers"
   (= 6 (add3 1 2 3))
   (:fails (add3 "hey"))
   (:fails (add3 1 2)))
  (+ x y z))

This compiles as normal. If you wish to run the tests in the (:tests ...) form, however, you need to turn testiere on.


Now if you try recompiling add3 those tests will be run.

This approach lets you add tests to functions without actually including the testiere source in your distributed code. You need only have testiere loaded and turned on during development.

You can, of course, turn testiere off too:


1.2Tests Expressions

Within the body of a (:tests ...) form are test expressions.

Expression Description
(:is form) The test fails if form evaluates to NIL.
(pred form1 form2) E.g (= (foo) 10) Provides more informative
error messages than :is
(:funcall function arg1 ...) Calls a function with some arguments. If this
function signals an error, then the test fails.
Useful when running several complext tests.
(:fails form) Evaluates form and expects it to singal an error.
If it does not signal an error, then the test fails.
(:signals condition form) Evaluates form and expects it to signal a
condition of type condition. If it does not, then
the test fails.
(:let bindings test1 ...) Runs test expressions in the context of some bound
(:with-defuns ((name args body) ...) tests ... ) Mimics labels syntax. Used for stubbing / mocking
functions will which have temporary definitions for
the duration of the :with-defuns form.
(:with-generic name methods tests ... ) Temporarily redefine the an entire generic
function for the duration of the enclosed
tests. methods is a list of forms, each of
is essentially anything that normally follows
(defmethod name ...).
E.g. ((x string) (string-upcase x)) or
(:after (x string) (print "after"))
(:do form) Evaluate form for its side effects. Useful
within a :let, :with-defuns, or :with-generic


(defpackage :testiere.examples
  (:use #:cl #:testiere))

(defpackage :dummy
  (:use #:cl))

(in-package :testiere.examples)

;;; Turn Testiere On.


(defun add3 (x y z)
  "Adds three numbers"
   (= 6 (add3 1 2 3))
   (:is (evenp (add3 2 2 2)))
   (:fails (add3))
   (:fails (add3 1 2 "oh no")))
  (+ x y z))

;;; Using external tests

(defun dummy::test-add10 (n)
  "Tests add10 in the same way N times. Obviously useless. We define
this in a separate package to give you an idea that you can embed
tests that aren't part of the package you're testing."
  (loop :repeat n :do 
    (assert (= 13 (add10 3)))))

(defun add10 (x)
  "Adds 10 to X"
   (:funcall 'dummy::test-add10 1))
  (+ x 10))

;;; Adding some context to tests with :LET

(defvar *count*)

(defun increment-count (&optional (amount 1))
  "Increments *COUNT* by AMOUNT"
   (:let ((*count* 5))
     (:do (increment-count))
     (= *count* 6)
     (:do (increment-count 4))
     (= *count* 10))
   (:let ((*count* -10))
     (= (increment-count) -9)))
  (incf *count* amount))

;;; Stubbing functions with :WITH-DEFUNS

(defun dummy::make-drakma-request (url)
  "Assume this actually makes an HTTP request using drakma"

(defun test-count-words-in-response ()
  (assert (= 3 (count-words-in-response "blah"))))

(defun count-words-in-response (url)
  "Fetches a url and counts the words in the response."
       ((dummy::make-drakma-request (url)
                                    "Hello     there    dudes"))
     (= 3 (count-words-in-response "dummy-url"))
     (:funcall 'test-count-words-in-response)))
    :with resp string := (dummy::make-drakma-request url)
    :with in-word? := nil
    :for char :across resp
    :when (and in-word? (not (alphanumericp char)))
      :count 1 :into wc
      :and :do (setf in-word? nil)
    :when (alphanumericp char)
      :do (setf in-word? t)
    :finally (return
               (if (alphanumericp char) (1+ wc) wc))))

;;; Testing Classes

(defclass point ()
    :accessor px
    :initform 0
    :initarg :x)
    :accessor py
    :initform 0
    :initarg :y))
   (:let ((pt (make-instance 'point :x 10 :y 20)))
     (= 20 (py pt))
     (= 10 (px pt))
     (:is (< (px pt) (py pt))))))

;;; Testing Structs

(defstruct pt
  x y
   (:let ((pt (make-pt :x 10 :y 20)))
     (= 20 (pt-y pt))
     (:is (< (pt-x pt) (pt-y pt))))))

;;; Testing Types

(deftype optional-int ()
   (:is (typep nil 'optional-int))
   (:is (typep 10 'optional-int))
   (:is (not (typep "foo" 'optional-int))))
  '(or integer null))

1.4How does it work?

Under the hood, testiere defines a custom *macroexpand-hook* that consults a registry of hooks. If a macro is found in the registery, tests are extracted and run whenever they appear. Otherwise the hook expands code normally.


Users can register testiere hooks by calling testiere:register-hook on three arguments:

  1. A symbol naming a macro
  2. A function designator for a function that extracts tests from amacro call (from the &whole of a macro call), returning themodified form and a list of the extracted test expressions. All ofthe built-ins hooks use the testiere::standard-extractor.
  3. An optional function accepting the same &whole of the macro call,and returning a list of restart handlers that are inserted as-isinto the body of a restart-case. See src/standard-hooks.lispfor examples.

Any macro that has been so registered will be available for testing at compile time.

Dependencies (1)

  • trivia

Dependents (0)

    • GitHub
    • Quicklisp