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To: homeier@cs.ucla.edu (peter v. homeier)
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Subject: Re: Question on Dijkstra Quote
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In-Reply-To: Your message of Tue, 16 May 1995 16:47:35 -0700. <9505162347.AA04588@oahu.cs.ucla.edu>
Date: Wed, 17 May 1995 10:33:00 +0100
From: Lawrence C Paulson <Larry.Paulson@cl.cam.ac.uk>
Message-Id: <"swan.cl.cam.:146400:950517093331"@cl.cam.ac.uk>

> Some time ago I heard that E. W. Dijkstra had once said or written
> something to the following effect:
> 
> "Testing is fine for showing the presence of errors; 
> but it is useless for showing their absence."
> 
> Try as I might, I have not been able to pin down the source of
> this quote.  Can anyone refer me to an article, book, etc. that I can
> reliably quote?  Also, what was the actual, literal quote?

It is on page 6 of 

@InCollection{dijkstra-notes,
  author = 	 "Edsger W. Dijkstra",
  title = 	 "Notes on Structured Programming",
  booktitle =	 "Structured Programming",
  publisher =	 "Academic Press",
  year =	 1972,
  editor =	 "O.-J. Dahl and E. W. Dijkstra and C. A. R. Hoare"}

The precise quote is

"Program testing can be used to show the presence of bugs, but never to show 
their absence!"

I recall that Dijkstra later objected that referring to errors as "bugs" 
diminishes their significance...

							Larry Paulson