Test::Warn(3pm)

1Warn(3)               User Contributed Perl Documentation              Warn(3)
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NAME

6       Test::Warn - Perl extension to test methods for warnings
7

SYNOPSIS

9         use Test::Warn;
10
11         warning_is    {foo(-dri => "/")} "Unknown Parameter 'dri'", "dri != dir gives warning";
12         warnings_are  {bar(1,1)} ["Width very small", "Height very small"];
13
14         warning_is    {add(2,2)} undef, "No warnings for calc 2+2"; # or
15         warnings_are  {add(2,2)} [],    "No warnings for calc 2+2"; # whichever reads better :-)
16
17         warning_like  {foo(-dri => "/")} qr/unknown param/i, "an unknown parameter test";
18         warnings_like {bar(1,1)} [qr/width.*small/i, qr/height.*small/i];
19
20         warning_is    {foo()} {carped => "didn't find the right parameters"};
21         warnings_like {foo()} [qr/undefined/,qr/undefined/,{carped => qr/no result/i}];
22
23         warning_like {foo(undef)}                 'uninitialized';
24         warning_like {bar(file => '/etc/passwd')} 'io';
25
26         warning_like {eval q/"$x"; $x;/}
27                      [qw/void uninitialized/],
28                      "some warnings at compile time";
29
30         warnings_exist {...} [qr/expected warning/], "Expected warning is thrown";
31

DESCRIPTION

33       A good style of Perl programming calls for a lot of diverse regression
34       tests.
35
36       This module provides a few convenience methods for testing warning
37       based-code.
38
39       If you are not already familiar with the Test::More manpage now would
40       be the time to go take a look.
41
42   FUNCTIONS
43       warning_is BLOCK STRING, TEST_NAME
44           Tests that BLOCK gives the specified warning exactly once.
45
46           The test fails if the BLOCK warns more than once or does not warn
47           at all.  If the string is undef, then the test succeeds if the
48           BLOCK doesn't give any warning.
49
50           Another way to say that there are no warnings in the block is:
51
52             warnings_are {foo()} [], "no warnings"
53
54           If you want to test for a warning given by Carp you have to write
55           something like:
56
57             warning_is {carp "msg"} {carped => 'msg'}, "Test for a carped warning";
58
59           The test will fail if a "normal" warning is found instead of a
60           "carped" one.
61
62           Note: "warn "foo"" would print something like "foo at -e line 1".
63           This method ignores everything after the "at". Thus to match this
64           warning you would have to call "warning_is {warn "foo"} "foo", "Foo
65           succeeded"".  If you need to test for a warning at an exact line,
66           try something like:
67
68             warning_like {warn "foo"} qr/at XYZ.dat line 5/
69
70           Warn messages with a trailing newline (like "warn "foo\n"") don't
71           produce the "at -e line 1" message by Perl.  Up to Test::Warn 0.30
72           such warning weren't supported by "warning_is {warn "foo\n"}
73           "foo\n"".  Starting with version 0.31 they are supported, but also
74           marked as experimental.
75
76           "warning_is()" and "warnings_are()" are only aliases to the same
77           method.  So you also could write "warning_is {foo()} [], "no
78           warning"" or something similar.
79
80           I decided to give two methods the same name to improve readability.
81
82           A true value is returned if the test succeeds, false otherwise.
83
84           The test name is optional, but recommended.
85
86       warnings_are BLOCK ARRAYREF, TEST_NAME
87           Tests to see that BLOCK gives exactly the specified warnings.  The
88           test fails if the warnings from BLOCK are not exactly the ones in
89           ARRAYREF.  If the ARRAYREF is equal to "[]", then the test succeeds
90           if the BLOCK doesn't give any warning.
91
92           Please read also the notes to "warning_is()" as these methods are
93           only aliases.
94
95           If you want more than one test for carped warnings, try this:
96
97             warnings_are {carp "c1"; carp "c2"} {carped => ['c1','c2'];
98
99           or
100
101             warnings_are {foo()} ["Warning 1", {carped => ["Carp 1", "Carp 2"]}, "Warning 2"];
102
103           Note that "{carped => ...}" must always be a hash ref.
104
105       warning_like BLOCK REGEXP, TEST_NAME
106           Tests that BLOCK gives exactly one warning and it can be matched by
107           the given regexp.
108
109           If the string is undef, then the tests succeeds if the BLOCK
110           doesn't give any warning.
111
112           The REGEXP is matched against the whole warning line, which in
113           general has the form "WARNING at __FILE__ line __LINE__".  So you
114           can check for a warning in the file "Foo.pm" on line 5 with:
115
116             warning_like {bar()} qr/at Foo.pm line 5/, "Testname"
117
118           I don't know whether it makes sense to do such a test :-(
119
120           However, you should be prepared as a matching with 'at', 'file',
121           '\d' or similar will always pass.
122
123           Consider "qr/^foo/" if you want to test for warning "foo something"
124           in file foo.pl.
125
126           You can also write the regexp in a string as "/.../" instead of
127           using the "qr/.../" syntax.
128
129           Note that the slashes are important in the string, as strings
130           without slashes are reserved for warning categories (to match
131           warning categories as can be seen in the perllexwarn man page).
132
133           Similar to "warning_is()" and "warnings_are()" you can test for
134           warnings via "carp" with:
135
136             warning_like {bar()} {carped => qr/bar called too early/i};
137
138           Similar to "warning_is()" and "warnings_are()",
139
140           "warning_like()" and "warnings_like()" are only aliases to the same
141           methods.
142
143           A true value is returned if the test succeeds, false otherwise.
144
145           The test name is optional, but recommended.
146
147       warning_like BLOCK STRING, TEST_NAME
148           Tests whether a BLOCK gives exactly one warning of the passed
149           category.
150
151           The categories are grouped in a tree, like it is expressed in
152           perllexwarn.  Also see "BUGS AND LIMITATIONS".
153
154           Thanks to the grouping in a tree, it's possible to test simply for
155           an 'io' warning, instead of testing for a
156           'closed|exec|layer|newline|pipe|unopened' warning.
157
158           Note, that warnings occurring at compile time can only be caught in
159           an eval block. So
160
161             warning_like {eval q/"$x"; $x;/}
162                           [qw/void uninitialized/],
163                           "some warnings at compile time";
164
165           will work, while it wouldn't work without the eval.
166
167           Note, that it isn't possible yet, to test for own categories,
168           created with warnings::register.
169
170       warnings_like BLOCK ARRAYREF, TEST_NAME
171           Tests to see that BLOCK gives exactly the number of the specified
172           warnings, in the defined order.
173
174           Please read also the notes to "warning_like()" as these methods are
175           only aliases.
176
177           Similar to "warnings_are()", you can test for multiple warnings via
178           "carp" and for warning categories, too:
179
180             warnings_like {foo()}
181                           [qr/bar warning/,
182                            qr/bar warning/,
183                            {carped => qr/bar warning/i},
184                            'io'
185                           ],
186                           "I hope you'll never have to write a test for so many warnings :-)";
187
188       warnings_exist BLOCK STRING|ARRAYREF, TEST_NAME
189           Same as warning_like, but will "warn()" all warnings that do not
190           match the supplied regex/category, instead of registering an error.
191           Use this test when you just want to make sure that specific
192           warnings were generated, and couldn't care less if other warnings
193           happened in the same block of code.
194
195             warnings_exist {...} [qr/expected warning/], "Expected warning is thrown";
196
197             warnings_exist {...} ['uninitialized'], "Expected warning is thrown";
198
199   EXPORT
200       "warning_is", "warnings_are", "warning_like", "warnings_like",
201       "warnings_exist" by default.
202

BUGS AND LIMITATIONS

204       Category check is done as "qr/category_name/". In some case this works,
205       like for category 'uninitialized'. For 'utf8' it does not work. Perl
206       does not have a list of warnings, so it is not possible to generate one
207       for "Test::Warn".
208
209       If you want to add a warning to a category, send a pull request.
210       Modifications should be done to %warnings_in_category. You should look
211       into perl source to check how warning is looking exactly.
212
213       Please note that warnings with newlines inside are very awkward.  The
214       only sensible way to handle them is to use the "warning_like" or
215       "warnings_like" methods. The background is that there is no really safe
216       way to distinguish between warnings with newlines and a stacktrace.
217
218       If a method has its own warn handler, overwriting $SIG{__WARN__}, my
219       test warning methods won't get these warnings.
220
221       The "warning_like BLOCK CATEGORY, TEST_NAME" method isn't fully tested.
222       Please take note if you use this this calling style, and report any
223       bugs you find.
224
225   XS warnings
226       As described in
227       https://rt.cpan.org/Ticket/Display.html?id=42070&results=3c71d1b101a730e185691657f3b02f21
228       or https://github.com/hanfried/test-warn/issues/1 XS warnings might not
229       be caught.
230

THANKS

235       Many thanks to Adrian Howard, chromatic and Michael G. Schwern, who
236       have given me a lot of ideas.
237

AUTHOR

239       Janek Schleicher, <bigj AT kamelfreund.de>
240

COPYRIGHT AND LICENSE

242       Copyright 2002 by Janek Schleicher
243
244       Copyright 2007-2014 by Alexandr Ciornii, <http://chorny.net/>
245
246       Copyright 2015-2018 by Janek Schleicher
247
248       This library is free software; you can redistribute it and/or modify it
249       under the same terms as Perl itself.
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253perl v5.34.0                      2021-07-23                           Warn(3)