Test::Prereq - check if Makefile.PL has the right pre-requisites


        # if you use Makefile.PL
        use Test::More;
        eval "use Test::Prereq";
        plan skip_all => "Test::Prereq required to test dependencies" if $@;

        # specify a perl version, test name, or module names to skip
        prereq_ok( $version, $name, \@skip );

        # if you use Module::Build
        use Test::More;
        eval "use Test::Prereq::Build";
        plan skip_all => "Test::Prereq::Build required to test dependencies" if $@;

        # or from the command line for a one-off check
        perl -MTest::Prereq -eprereq_ok

    #The prerequisites test take quite some time so the following construct is
    #recommended for non-author testers
        use Test::More;
        eval "use Test::Prereq::Build";

        my $msg;
        if ($@) {
            $msg = 'Test::Prereq::Build required to test dependencies';
        } elsif (not $ENV{TEST_AUTHOR}) {
            $msg = 'Author test.  Set $ENV{TEST_AUTHOR} to a true value to run.';
        plan skip_all => $msg if $msg;


The prereq_ok() function examines the modules it finds in blib/lib/, blib/script, and the test files it finds in t/ (and It figures out which modules they use and compares that list of modules to those in the PREREQ_PM section of Makefile.PL.

If you use Module::Build instead, see Test::Prereq::Build instead.

Warning about redefining ExtUtils::MakeMaker::WriteMakefile

Test::Prereq has its own version of ExtUtils::MakeMaker::WriteMakefile so it can run the Makefile.PL and get the argument list of that function. You may see warnings about this.


prereq_ok( [ VERSION, [ NAME [, SKIP_ARRAY] ] ] )

Tests Makefile.PL to ensure all non-core module dependencies are in PREREQ_PM. If you haven't set a testing plan already, prereq_ok() creates a plan of one test.

If you don't specify a version, prereq_ok assumes you want to compare the list of prerequisite modules to the version of perl running the test.

Valid versions come from Module::CoreList (which uses $]).

        use Module::CoreList;
        print map "$_\n", sort keys %Module::CoreList::version;

prereq_ok attempts to remove modules found in lib/ and libraries found in t/ from the reported prerequisites.

The optional third argument is an array reference to a list of names that prereq_ok should ignore. You might want to use this if your tests do funny things with require.

Versions prior to 1.038 would use to virtually include prerequisites in distributions that you declared explicitly. This isn't really a good idea. Some modules have moved to different distributions, so you should just specify all the modules that you use instead of relying on a particular distribution to provide them. Not only that, expanding distributions with takes forever.

If you want the old behavior, set the TEST_PREREQ_EXPAND_WITH_CPAN environment variable to a true value.


  • set up a couple fake module distributions to test

  • warn about things that show up in PREREQ_PM unnecessarily


This source is in Github:


Many thanks to:

Andy Lester, Slavin Rezić, Randal Schwartz, Iain Truskett, Dylan Martin


brian d foy, <>


Copyright © 2002-2016, brian d foy <>. All rights reserved. This software is available under the Artistic License 2.