Provided by: libtest-warnings-perl_0.026-1_all bug


       Test::Warnings - Test for warnings and the lack of them


       version 0.026


           use Test::More;
           use Test::Warnings;


       emits TAP:

           ok 1 - yay!
           ok 2 - no (unexpected) warnings (via done_testing)


           use Test::More tests => 3;
           use Test::Warnings 0.005 ':all';

           like(warning { warn "oh noes!" }, qr/^oh noes/, 'we warned');

       emits TAP:

           ok 1 - yay!
           ok 2 - we warned
           ok 3 - no (unexpected) warnings (via END block)


       If you've ever tried to use Test::NoWarnings to confirm there are no warnings generated by
       your tests, combined with the convenience of "done_testing" to not have to declare a test
       count, you'll have discovered that these two features do not play well together, as the
       test count will be calculated before the warnings test is run, resulting in a TAP error.
       (See "examples/" in this distribution for a demonstration.)

       This module is intended to be used as a drop-in replacement for Test::NoWarnings: it also
       adds an extra test, but runs this test before "done_testing" calculates the test count,
       rather than after.  It does this by hooking into "done_testing" as well as via an "END"
       block.  You can declare a plan, or not, and things will still Just Work.

       It is actually equivalent to:

           use Test::NoWarnings 1.04 ':early';

       as warnings are still printed normally as they occur.  You are safe, and enthusiastically
       encouraged, to perform a global search-replace of the above with "use Test::Warnings;"
       whether or not your tests have a plan.

       It can also be used as a replacement for Test::Warn, if you wish to test the content of
       expected warnings; read on to find out how.


       The following functions are available for import (not included by default; you can also
       get all of them by importing the tag ":all"):

   "allow_warnings([bool])" - EXPERIMENTAL - MAY BE REMOVED
       When passed a true value, or no value at all, subsequent warnings will not result in a
       test failure; when passed a false value, subsequent warnings will result in a test
       failure.  Initial value is "false".

       When warnings are allowed, any warnings will instead be emitted via Test::Builder::note.

   "allowing_warnings" - EXPERIMENTAL - MAY BE REMOVED
       Returns whether we are currently allowing warnings (set by "allow_warnings" as described

   "had_no_warnings(<optional test name>)"
       Tests whether there have been any warnings so far, not preceded by an "allowing_warnings"
       call.  It is run automatically at the end of all tests, but can also be called manually at
       any time, as often as desired.

   "warnings( { code } )"
       Given a code block, runs the block and returns a list of all the (not previously allowed
       via "allow_warnings") warnings issued within.  This lets you test for the presence of
       warnings that you not only would allow, but must be issued.  Testing functions are not
       provided; given the strings returned, you can test these yourself using your favourite
       testing functions, such as Test::More::is or Test::Deep::cmp_deeply.

       You can use this construct as a replacement for Test::Warn::warnings_are:

               [ warnings { ... } ],
                   'warning message 1',
                   'warning message 2',
               'got expected warnings',

       or, to replace Test::Warn::warnings_like:

               [ warnings { ... } ],
               bag(    # ordering of messages doesn't matter
                   re(qr/warning message 1/),
                   re(qr/warning message 2/),
               'got expected warnings (in any order)',

       Warnings generated by this code block are NOT propagated further. However, since they are
       returned from this function with their filename and line numbers intact, you can re-issue
       them yourself immediately after calling "warnings(...)", if desired.

       Note that "use Test::Warnings 'warnings'" will give you a "warnings" subroutine in your
       namespace (most likely "main", if you're writing a test), so you (or things you load)
       can't subsequently do "warnings->import" -- it will result in the error: "Not enough
       arguments for Test::Warnings::warnings at ..., near "warnings->import"".  To work around
       this, either use the fully-qualified form ("Test::warnings") or make your calls to the
       "warnings" package first.

   "warning( { code } )"
       Same as "warnings( { code } )", except a scalar is always returned - the single warning
       produced, if there was one, or an arrayref otherwise -- which can be more convenient to
       use than "warnings()" if you are expecting exactly one warning.

       However, you are advised to capture the result from "warning()" into a temp variable so
       you can dump its value if it doesn't contain what you expect.  e.g. with this test:

               warning { foo() },
               qr/^this is a warning/,
               'got a warning from foo()',

       if you get two warnings (or none) back instead of one, you'll get an arrayref, which will
       result in an unhelpful test failure message like:

           #   Failed test 'got a warning from foo()'
           #   at t/mytest.t line 10.
           #                   'ARRAY(0xdeadbeef)'
           #     doesn't match '(?^:^this is a warning)'

       So instead, change your test to:

           my $warning = warning { foo() };
               qr/^this is a warning/,
               'got a warning from foo()',
           ) or diag 'got warning(s): ', explain($warning);


       Imports all functions listed above

       Disables the addition of a "had_no_warnings" test via "END" or "done_testing"


       Sometimes new warnings can appear in Perl that should not block installation -- for
       example, smartmatch was recently deprecated in perl 5.17.11, so now any distribution that
       uses smartmatch and also tests for warnings cannot be installed under 5.18.0.  You might
       want to consider only making warnings fail tests in an author environment -- you can do
       this with the if pragma:

           use if $ENV{AUTHOR_TESTING} || $ENV{RELEASE_TESTING}, 'Test::Warnings';

       In future versions of this module, when interfaces are added to test the content of
       warnings, there will likely be additional sugar available to indicate that warnings should
       be checked only in author tests (or TODO when not in author testing), but will still
       provide exported subs.  Comments are enthusiastically solicited - drop me an email, write
       up an RT ticket, or come by "#perl-qa" on irc!

       Achtung!  This is not a great idea:

           sub warning_like(&$;$) {
               my ($code, $pattern, $name) = @_;
               like( &warning($code), $pattern, $name );

           warning_like( { ... }, qr/foo/, 'foo appears in the warning' );

       If the code in the "{ ... }" is going to warn with a stack trace with the arguments to
       each subroutine in its call stack (for example via "Carp::cluck"), the test name, "foo
       appears in the warning" will itself be matched by the regex (see examples/warning_like.t).
       Instead, write this:

         like( warning { ... }, qr/foo/, 'foo appears in the warning' );


       ·   "allow_warnings(qr/.../)" - allow some warnings and not others

       ·   more sophisticated handling in subtests - if we save some state on the Test::Builder
           object itself, we can allow warnings in a subtest and then the state will revert when
           the subtest ends, as well as check for warnings at the end of every subtest via

       ·   sugar for making failures TODO when testing outside an author environment


       ·   Test::NoWarnings

       ·   Test::FailWarnings

       · YANWT (Yet Another No-Warnings Tester)

       ·   strictures - which makes all warnings fatal in tests, hence lessening

           the need for special warning testing

       ·   Test::Warn

       ·   Test::Fatal


       Bugs may be submitted through the RT bug tracker
       <> (or <>).

       There is also a mailing list available for users of this distribution, at

       There is also an irc channel available for users of this distribution, at

       I am also usually active on irc, as 'ether' at "".


       Karen Etheridge <>


       A. Sinan Unur <>


       This software is copyright (c) 2013 by Karen Etheridge.

       This is free software; you can redistribute it and/or modify it under the same terms as
       the Perl 5 programming language system itself.