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Test::DependentModules - Test all modules which depend on your module


version 0.27


    use Test::DependentModules qw( test_all_dependents );


    # or ...

    use Test::DependentModules qw( test_modules );
    use Test::More tests => 3;

    test_modules( 'Exception::Class', 'DateTime', 'Log::Dispatch' );


WARNING: The tests this module does should never be run as part of a normal CPAN install!

This module is intended as a tool for module authors who would like to easily test that a module release will not break dependencies. This is particularly useful for module authors (like myself) who have modules which are a dependency of many other modules.

How It Works

Internally, this module will download dependencies from CPAN and run their tests. If those dependencies in turn have unsatisfied dependencies, they are installed into a temporary directory. These second-level (and third-, etc) dependencies are not tested.

In order to avoid prompting, this module sets $ENV{PERL_AUTOINSTALL} to --defaultdeps and sets $ENV{PERL_MM_USE_DEFAULT} to a true value.

Nonetheless, some ill-behaved modules will still wait for a prompt. Unfortunately, because of the way this module attempts to keep output to a minimum, you won't see these prompts. Patches are welcome.

Running Tests in Parallel

If you're testing a lot of modules, you might benefit from running tests in parallel. You'll need to have Parallel::ForkManager installed for this to work.

Set the $ENV{PERL_TEST_DM_PROCESSES} env var to a value greater than 1 to enable parallel testing.


This module optionally exports three functions:

test_all_dependents( $module, { filter => sub { ... } } )

Given a module or distro name, this function uses MetaCPAN::Client to find all its dependencies and test them. It will set a test plan for you.

If you provide a filter sub, it will be called with a single argument, the distribution name, which will be something like "Test-DependentModules" (note the lack of colons). The filter should return a true or false value to indicate whether or not to test that distribution.

If you don't provide a filter, you can provide a regex to use by passing an exclude key in the hashref. Anything that matches the regex is excluded.

Additionally, any distribution name starting with "Task" or "Bundle" is always excluded.


Given a list of module names, this function will test them all. You can use this if you'd prefer to hard code a list of modules to test.

In this case, you will have to handle your own test planning.


DEPRECATED. Use the test_modules() sub instead, so you can optionally run tests in parallel.

Given a module name, this function will test it. You can use this if you'd prefer to hard code a list of modules to test.

In this case, you will have to handle your own test planning.


If you want to include a module-to-be-released in the path seen by dependencies, you must make sure that the correct path ends up in $ENV{PERL5LIB}. If you use prove -l or prove -b to run tests, then that will happen automatically.


By default, this module attempts to quiet down CPAN and the module building toolchain as much as possible. However, when there are test failures in a dependency it's nice to see the output.

In addition, if the tests spit out warnings but still pass, this will just be treated as a pass.

If you enable logging, this module log all successes, warnings, and failures, along with the full output of the test suite for each dependency. In addition, it logs what prereqs it installs, since you may want to install some of them permanently to speed up future tests.

To enable logging, you must provide a directory to which log files will be written. The log file names are of the form test-my-deps-$$-$type.log, where $type is one of "status", "error", or "prereq".

The directory should be provided in $ENV{PERL_TEST_DM_LOG_DIR}. The directory must already exist.

You also can enable verbose output from the CPAN package by setting the $ENV{PERL_TEST_DM_CPAN_VERBOSE} variable to a true value.


Bugs may be submitted at or via email to

I am also usually active on IRC as 'autarch' on irc://


The source code repository for Test-DependentModules can be found at


If you'd like to thank me for the work I've done on this module, please consider making a "donation" to me via PayPal. I spend a lot of free time creating free software, and would appreciate any support you'd care to offer.

Please note that I am not suggesting that you must do this in order for me to continue working on this particular software. I will continue to do so, inasmuch as I have in the past, for as long as it interests me.

Similarly, a donation made in this way will probably not make me work on this software much more, unless I get so many donations that I can consider working on free software full time (let's all have a chuckle at that together).

To donate, log into PayPal and send money to, or use the button at


Dave Rolsky <>


  • Graham Knop <>

  • Jesse Luehrs <>

  • mickey <>

  • Olaf Alders <>

  • Sawyer X <>


This software is Copyright (c) 2019 by Dave Rolsky.

This is free software, licensed under:

  The Artistic License 2.0 (GPL Compatible)

The full text of the license can be found in the LICENSE file included with this distribution.