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Test::FailWarnings(3) User Contributed Perl Documentation Test::FailWarnings(3)


Test::FailWarnings - Add test failures if warnings are caught


version 0.008


Test file:

    use strict;
    use warnings;
    use Test::More;
    use Test::FailWarnings;
    ok( 1, "first test" );
    ok( 1 + "lkadjaks", "add non-numeric" );


    ok 1 - first test
    not ok 2 - Test::FailWarnings should catch no warnings
    #   Failed test 'Test::FailWarnings should catch no warnings'
    #   at t/bin/ line 7.
    # Warning was 'Argument "lkadjaks" isn't numeric in addition (+) at t/bin/ line 7.'
    ok 3 - add non-numeric
    # Looks like you failed 1 test of 3.


This module hooks $SIG{__WARN__} and converts warnings to Test::More fail() calls. It is designed to be used with "done_testing", when you don't need to know the test count in advance.

Just as with Test::NoWarnings, this does not catch warnings if other things localize $SIG{__WARN__}, as this is designed to catch unhandled warnings.


Overriding $SIG{__WARN__}

On "import", $SIG{__WARN__} is replaced with "Test::FailWarnings::handler".

    use Test::FailWarnings;  # global

If you don't want global replacement, require the module instead and localize in whatever scope you want.

    require Test::FailWarnings;
        local $SIG{__WARN__} = \&Test::FailWarnings::handler;
        # ... warnings will issue fail() here

When the handler reports on the source of the warning, it will look past any calling packages starting with "Carp" or "warnings" to try to detect the real origin of the warning.

Allowing warnings from dependencies

If you want to ignore failures from outside your own code, you can set $Test::FailWarnings::ALLOW_DEPS to a true value. You can do that on the "use" line with "-allow_deps".

    use Test::FailWarnings -allow_deps => 1;

When true, warnings will only be thrown if they appear to originate from a filename matching "qr/^(?:t|xt|lib|blib)/"

Allowing warnings from specific modules

If you want to white-list specific modules only, you can add their package names to @Test::NoWarnings::ALLOW_FROM. You can do that on the "use" line with "-allow_from".

    use Test::FailWarnings -allow_from => [ qw/Annoying::Module/ ];


  • Test::NoWarnings -- catches warnings and reports in an "END" block. Not (yet) friendly with "done_testing".
  • Test::Warnings -- a replacement for Test::NoWarnings that works with done_testing
  • Test::Warn -- test for warnings without triggering failures from this modules


Bugs / Feature Requests

Please report any bugs or feature requests through the issue tracker at <>. You will be notified automatically of any progress on your issue.

Source Code

This is open source software. The code repository is available for public review and contribution under the terms of the license.


  git clone


David Golden <>


This software is Copyright (c) 2013 by David Golden.

This is free software, licensed under:

  The Apache License, Version 2.0, January 2004
2013-10-04 perl v5.38.2