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Test::LectroTest::TutoUser(Contributed Perl DocumTest::LectroTest::Tutorial(3)

NAME
       Test::LectroTest::Tutorial - How	to use LectroTest to test your
       software

VERSION
       version 0.5001

SYNOPSIS
       LectroTest is an	automated, specification-based testing system.	To use
       it, declare properties that specify the expected	behavior of your
       software.  Then invoke LectroTest to test whether those properties
       hold.

       LectroTest does this by running repeated	random trials against your
       software.  If LectroTest	finds that a property doesn't hold, it emits
       the counterexample that "broke" your software.  You can then plug the
       counterexample into your	software to debug the problem.	(It's also a
       good idea to add	the counterexample to your list	of regression tests.)

OVERVIEW
       Think of	your software's	behavior as a haystack that you're searching
       for needles.  Each error	is a needle.  You want to find the needles and
       remove of them.	LectroTest will	search the haystack for	you -- it's
       nice that way --	but first you must tell	it about the shape of the
       haystack	and how	to recognize a needle when it sees one.

   The Haystack
       The shape of the	haystack is defined by a set of	"generator bindings,"
       in which	variables are bound to the output of value generators:

	 x <- Int, c <-	Char( charset=>"A-Z" )

       The above can be	read, "For all integers	x and all characters c in the
       range A through Z."  The	idea is	that each unique instance of the pair
       (x, c) specifies	a point	in the haystack	that we	can search for
       needles.

   The Needle Recognizer
       The "needle recognizer" is defined by a snippet of code that uses the
       bound variables to inspect a given point	in the haystack.  It returns a
       "thumbs up" (true) if the point is free of needles or a "thumbs down"
       (false) if it finds a needle:

	 the_thing_we_are_testing($x, $c) >= 0;

       The above asserts for each point	in the haystack	that the output	of the
       function	"the_thing_we_are_testing" must	be non-negative.

   Put them together to	make a Property
       The generator bindings and needle recognizer are	combined to make a
       property:

	 Property {
	   ##[ x <- Int, c <- Char( charset=>"A-Z" ) ]##
	   the_thing_we_are_testing($x,	$c) >= 0;
	 }, name => "the_thing_we_are_testing(...) is non-negative";

       You'll note that	we also	added a	meaningful name.  Although not
       strictly	required, it's an excellent practice that makes	life easier.
       (You'll also note that we placed	the generator bindings inside of the
       magic delimiters	"##[ ]##".  This tells Perl that our bindings are
       bindings	and not	regular	Perl code.)

       We can read the above property like so: "For all	integers x and all
       characters c in the range A through Z, we assert	that
       "the_thing_we_are_testing" is non-negative."

   Testing whether your	Properties hold
       After you define	properties for your software, just add them to a small
       Perl program that uses the Test::LectroTest module:

	 # MyProperties.l.t

	 use MyModule;	# provides the_thing_we_are_testing
	 use Test::LectroTest;

	 Property {
	   ##[ x <- Int, c <- Char( charset=>"A-Z" ) ]##
	   the_thing_we_are_testing($x,	$c) >= 0;
	 }, name => "the_thing_we_are_testing(...) is non-negative";

       Then you	can test your properties simply	by running the program:

	 $ perl	MyProperties.l.t

       If your properties check	out, you'll see	something like this:

	 1..1
	 ok 1 -	'the_thing_we_are_testing(...) is non-negative'	(1000 attempts)

       If something goes wrong,	however, LectroTest will tell you where	it
       happened:

	 1..1
	 not ok	1 - 'the_thing_we_are_testing(...) is non-negative' \
	   falsified in	23 attempts
	 # Counterexample:
	 # $x =	4
	 # $c =	"R"

       What this says is that at the point (x=4, c="R")	in the haystack, there
       is a needle (i.e., your property	doesn't	hold).	With this information,
       you can examine your code to determine the cause	of the error.

LET'S DO IT!
       Now that	we have	big-picture understanding of "LectroTesting," let's
       try a few examples together.

       [TODO: write the	step-by-step tutorial examples.	 For now, take a look
       at the slides from my LectroTest	talk for two such examples.  The
       slides are available at the LectroTest Home.]

SEE ALSO
       Test::LectroTest	gives a	quick overview of automatic, specification-
       based testing with LectroTest.

       Test::LectroTest::Property explains in detail what you can put inside
       of your property	specifications.

       Test::LectroTest::Generator describes the many generators and generator
       combinators that	you can	use to define the shapes of the	haystacks you
       encounter during	your testing adventures.

       Test::LectroTest::TestRunner describes the objects that check your
       properties and tells you	how to turn their control knobs.  You'll want
       to look here if you're interested in customizing	the testing procedure.

AUTHOR
       Tom Moertel (tom@moertel.com)

INSPIRATION
       The LectroTest project was inspired by Haskell's	QuickCheck module by
       Koen Claessen and John Hughes:
       http://www.cs.chalmers.se/~rjmh/QuickCheck/.

COPYRIGHT and LICENSE
       Copyright (c) 2004-13 by	Thomas G Moertel.  All rights reserved.

       This program is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.

perl v5.32.1			  2013-05-16	 Test::LectroTest::Tutorial(3)

NAME | VERSION | SYNOPSIS | OVERVIEW | LET'S DO IT! | SEE ALSO | AUTHOR | INSPIRATION | COPYRIGHT and LICENSE

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