1Test::LectroTest(3) User Contributed Perl Documentation Test::LectroTest(3)
2
6 Test::LectroTest - Easy, automatic, specification-based tests
7
9 version 0.5001
10
12 #!/usr/bin/perl -w
13 use MyModule; # contains code we want to test
15 use Test::LectroTest;
16 Property {
18 ##[ x <- Int, y <- Int ]##
19 MyModule::my_function( $x, $y ) >= 0;
20 }, name => "my_function output is non-negative" ;
21 Property { ... }, name => "yet another property" ;
23 # more properties to check here
25
27 This module provides a simple (yet full featured) interface to
28 LectroTest, an automated, specification-based testing system for Perl.
29 To use it, declare properties that specify the expected behavior of
30 your software. LectroTest then checks your software to see whether
31 those properties hold.
32 Declare properties using the "Property" function, which takes a block
34 of code and promotes it to a Test::LectroTest::Property:
35 Property {
37 ##[ x <- Int, y <- Int ]##
38 MyModule::my_function( $x, $y ) >= 0;
39 }, name => "my_function output is non-negative" ;
40 The first part of the block must contain a generator-binding
42 declaration. For example:
43 ##[ x <- Int, y <- Int ]##
45 (Note the special bracketing, which is required.) This particular
47 binding says, "For all integers x and y." (By the way, you aren't
48 limited to integers. LectroTest also gives you booleans, strings,
49 lists, hashes, and more, and it lets you define your own generator
50 types. See Test::LectroTest::Generator for more.)
51 The second part of the block is simply a snippet of code that makes use
53 of the variables we bound earlier to test whether a property holds for
54 the piece of software we are testing:
55 MyModule::my_function( $x, $y ) >= 0;
57 In this case, it asserts that "MyModule::my_function($x,$y)" returns a
59 non-negative result. (Yes, $x and $y refer to the same x and y that we
60 bound to the generators earlier. LectroTest automagically loads these
61 lexically bound Perl variables with values behind the scenes.)
62 Note: If you want to use testing assertions like "ok" from Test::Simple
64 or "is", "like", or "cmp_ok" from Test::More (and the related family of
65 Test::Builder-based testing modules), see Test::LectroTest::Compat,
66 which lets you mix and match LectroTest with these modules.
67 Finally, we give the whole Property a name, in this case "my_function
69 output is non-negative." It's a good idea to use a meaningful name
70 because LectroTest refers to properties by name in its output.
71 Let's take a look at the finished property specification:
73 Property {
75 ##[ x <- Int, y <- Int ]##
76 MyModule::my_function( $x, $y ) >= 0;
77 }, name => "my_function output is non-negative" ;
78 It says, "For all integers x and y, we assert that my_function's output
80 is non-negative."
81 To check whether this property holds, simply put it in a Perl program
83 that uses the Test::LectroTest module. (See the "SYNOPSIS" for an
84 example.) When you run the program, LectroTest will load the property
85 (and any others in the file) and check it by running random trials
86 against the software you're testing.
87 Note: If you want to place LectroTest property checks into a test plan
89 managed by Test::Builder-based modules such as Test::Simple or
90 Test::More, see Test::LectroTest::Compat.
91 If LectroTest is able to "break" your software during the property
93 check, it will emit a counterexample to your property's assertions and
94 stop. You can plug the counterexample back into your software to debug
95 the problem. (You might also want to add the counterexample to a list
96 of regression tests.)
97 A successful LectroTest looks like this:
99 1..1
101 ok 1 - 'my_function output is non-negative' (1000 attempts)
102 On the other hand, if you're not so lucky:
104 1..1
106 not ok 1 - 'my_function output is non-negative' falsified \
107 in 324 attempts
108 # Counterexample:
109 # $x = -34
110 # $y = 0
111
113 The exit code returned by running a suite of property checks is the
114 number of failed checks. The code is 0 if all properties passed their
115 checks or N if N properties failed. (If more than 254 properties
116 failed, the exit code will be 254.)
117
119 There is one testing parameter (among others) that you might wish to
120 change from time to time: the number of trials to run for each property
121 checked. By default it is 1,000. If you want to try more or fewer
122 trials, pass the "trials=>"N flag:
123 use Test::LectroTest trials => 10_000;
125
127 LectroTest can record failure-causing test cases to a file, and it can
128 play those test cases back as part of its normal testing strategy. The
129 easiest way to take advantage of this feature is to set the regressions
130 parameter when you "use" this module:
131 use Test::LectroTest
133 regressions => "regressions.txt";
134 This tells LectroTest to use the file "regressions.txt" for both
136 recording and playing back failures. If you want to record and play
137 back from separate files, or want only to record or play back, use the
138 record_failures and/or playback_failures options:
139 use Test::LectroTest
141 playback_failures => "regression_suite_for_my_module.txt",
142 record_failures => "failures_in_the_field.txt";
143 See Test::LectroTest::RegressionTesting for more.
145
147 When you use this module, it imports all of the generator-building
148 functions from Test::LectroTest::Generator into the your code's
149 namespace. This is almost always what you want, but I figured I ought
150 to say something about it here to reduce the possibility of surprise.
151 A Property specification must appear in the first column, i.e., without
153 any indentation, in order for it to be automatically loaded and
154 checked. If this poses a problem, let me know, and this restriction
155 can be lifted.
156
158 For a gentle introduction to LectroTest, see
159 Test::LectroTest::Tutorial. Also, the slides from my LectroTest talk
160 for the Pittsburgh Perl Mongers make for a great introduction.
161 Download a copy from the LectroTest home (see below).
162 Test::LectroTest::RegressionTesting explains how to test for
164 regressions and corner cases using LectroTest.
165 Test::LectroTest::Compat lets you mix LectroTest with the popular
167 family of Test::Builder-based modules such as Test::Simple and
168 Test::More.
169 Test::LectroTest::Property explains in detail what you can put inside
171 of your property specifications.
172 Test::LectroTest::Generator describes the many generators and generator
174 combinators that you can use to define the test or condition space that
175 you want LectroTest to search for bugs.
176 Test::LectroTest::TestRunner describes the objects that check your
178 properties and tells you how to turn their control knobs. You'll want
179 to look here if you're interested in customizing the testing procedure.
180
182 The LectroTest home is http://community.moertel.com/LectroTest. There
183 you will find more documentation, presentations, mailing-list archives,
184 a wiki, and other helpful LectroTest-related resources. It's also the
185 best place to ask questions.
186
188 Tom Moertel (tom@moertel.com)
189
191 The LectroTest project was inspired by Haskell's QuickCheck module by
192 Koen Claessen and John Hughes:
193 http://www.cs.chalmers.se/~rjmh/QuickCheck/.
194
196 Copyright (c) 2004-05 by Thomas G Moertel. All rights reserved.
197 This program is free software; you can redistribute it and/or modify it
199 under the same terms as Perl itself.
200perl v5.34.0 2021-07-23 Test::LectroTest(3)