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Tuesday, January 27, 2004

A thread of conversation on the agile-testing yahoo group is speculating on the ability to define a function and its tests "contiguously" to reduce the effort to make the contextual switch between "coding" and "testing".

Here is a simple Scheme macro to approximate the idea...

; The following is a macro that allows you to supply test input and
; test results when you define a function. After the function is
; defined, the tool automatically runs the function on the test input
; and checks to see if it matches the expected result. There are a
; number of enhancements (list of test inputs, define test function,
; etc.) to consider. 

(defmacro define-eg (name-result parameter-input . body)
  (let ((name (car name-result))
 	(eg-result (cadr name-result))
 	(parameters (map (lambda (p) (car p)) parameter-input))
 	(eg-input (map (lambda (p) (cadr p)) parameter-input)))
    `(begin (define (,name ,@parameters)
 	      ,@body)
 	    (equal? ,eg-result (,name ,@eg-input)))))
 
(define-eg (product-of-sums 108) ((a 5) (b 7) (c 9))
  (* (+ a b) c))
 
> (load "define-eg.scm")
> (define-eg (product-of-sums 108) ((a 5) (b 7) (c 9)) (* (+ a b) c))
#t
> (product-of-sums 5 7 9)
108
> (define-eg (bad-product-of-sums 108) ((a 5) (b 7) (c 9)) (+ (* a b) c))
#f
> (bad-product-of-sums 5 7 9)
44

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Portland, Oregon, United States
I'm usually writing from my favorite location on the planet, the pacific northwest of the u.s. I write for myself only and unless otherwise specified my posts here should not be taken as representing an official position of my employer. Contact me at my gee mail account, username patrickdlogan.