1Test::LectroTest::TutorUisaelr(3C)ontributed Perl DocumeTnetsatt:i:oLnectroTest::Tutorial(3)
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NAME

6       Test::LectroTest::Tutorial - How to use LectroTest to test your
7       software
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VERSION

10       version 0.5001
11

SYNOPSIS

13       LectroTest is an automated, specification-based testing system.  To use
14       it, declare properties that specify the expected behavior of your
15       software.  Then invoke LectroTest to test whether those properties
16       hold.
17
18       LectroTest does this by running repeated random trials against your
19       software.  If LectroTest finds that a property doesn't hold, it emits
20       the counterexample that "broke" your software.  You can then plug the
21       counterexample into your software to debug the problem.  (It's also a
22       good idea to add the counterexample to your list of regression tests.)
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OVERVIEW

25       Think of your software's behavior as a haystack that you're searching
26       for needles.  Each error is a needle.  You want to find the needles and
27       remove of them.  LectroTest will search the haystack for you -- it's
28       nice that way -- but first you must tell it about the shape of the
29       haystack and how to recognize a needle when it sees one.
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31   The Haystack
32       The shape of the haystack is defined by a set of "generator bindings,"
33       in which variables are bound to the output of value generators:
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35         x <- Int, c <- Char( charset=>"A-Z" )
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37       The above can be read, "For all integers x and all characters c in the
38       range A through Z."  The idea is that each unique instance of the pair
39       (x, c) specifies a point in the haystack that we can search for
40       needles.
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42   The Needle Recognizer
43       The "needle recognizer" is defined by a snippet of code that uses the
44       bound variables to inspect a given point in the haystack.  It returns a
45       "thumbs up" (true) if the point is free of needles or a "thumbs down"
46       (false) if it finds a needle:
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48         the_thing_we_are_testing($x, $c) >= 0;
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50       The above asserts for each point in the haystack that the output of the
51       function "the_thing_we_are_testing" must be non-negative.
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53   Put them together to make a Property
54       The generator bindings and needle recognizer are combined to make a
55       property:
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57         Property {
58           ##[ x <- Int, c <- Char( charset=>"A-Z" ) ]##
59           the_thing_we_are_testing($x, $c) >= 0;
60         }, name => "the_thing_we_are_testing(...) is non-negative";
61
62       You'll note that we also added a meaningful name.  Although not
63       strictly required, it's an excellent practice that makes life easier.
64       (You'll also note that we placed the generator bindings inside of the
65       magic delimiters "##[ ]##".  This tells Perl that our bindings are
66       bindings and not regular Perl code.)
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68       We can read the above property like so: "For all integers x and all
69       characters c in the range A through Z, we assert that
70       "the_thing_we_are_testing" is non-negative."
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72   Testing whether your Properties hold
73       After you define properties for your software, just add them to a small
74       Perl program that uses the Test::LectroTest module:
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76         # MyProperties.l.t
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78         use MyModule;  # provides the_thing_we_are_testing
79         use Test::LectroTest;
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81         Property {
82           ##[ x <- Int, c <- Char( charset=>"A-Z" ) ]##
83           the_thing_we_are_testing($x, $c) >= 0;
84         }, name => "the_thing_we_are_testing(...) is non-negative";
85
86       Then you can test your properties simply by running the program:
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88         $ perl MyProperties.l.t
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90       If your properties check out, you'll see something like this:
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92         1..1
93         ok 1 - 'the_thing_we_are_testing(...) is non-negative' (1000 attempts)
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95       If something goes wrong, however, LectroTest will tell you where it
96       happened:
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98         1..1
99         not ok 1 - 'the_thing_we_are_testing(...) is non-negative' \
100           falsified in 23 attempts
101         # Counterexample:
102         # $x = 4
103         # $c = "R"
104
105       What this says is that at the point (x=4, c="R") in the haystack, there
106       is a needle (i.e., your property doesn't hold).  With this information,
107       you can examine your code to determine the cause of the error.
108

LET'S DO IT!

110       Now that we have big-picture understanding of "LectroTesting," let's
111       try a few examples together.
112
113       [TODO: write the step-by-step tutorial examples.  For now, take a look
114       at the slides from my LectroTest talk for two such examples.  The
115       slides are available at the LectroTest Home.]
116

SEE ALSO

118       Test::LectroTest gives a quick overview of automatic, specification-
119       based testing with LectroTest.
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121       Test::LectroTest::Property explains in detail what you can put inside
122       of your property specifications.
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124       Test::LectroTest::Generator describes the many generators and generator
125       combinators that you can use to define the shapes of the haystacks you
126       encounter during your testing adventures.
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128       Test::LectroTest::TestRunner describes the objects that check your
129       properties and tells you how to turn their control knobs.  You'll want
130       to look here if you're interested in customizing the testing procedure.
131

AUTHOR

133       Tom Moertel (tom@moertel.com)
134

INSPIRATION

136       The LectroTest project was inspired by Haskell's QuickCheck module by
137       Koen Claessen and John Hughes:
138       http://www.cs.chalmers.se/~rjmh/QuickCheck/.
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141       Copyright (c) 2004-13 by Thomas G Moertel.  All rights reserved.
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143       This program is free software; you can redistribute it and/or modify it
144       under the same terms as Perl itself.
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148perl v5.30.1                      2020-01-30     Test::LectroTest::Tutorial(3)
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