IPC::System::Simple is required to run the test suite.  The following
additional Perl modules will be used by the test suite if present:

* Devel::Cover
* Test::MinimumVersion
* Test::Perl::Critic
* Test::Pod
* Test::Pod::Coverage
* Test::Spelling
* Test::Strict
* Test::Synopsis

All are available on CPAN.  Those tests will be skipped if the modules are
not available.
