tizatron has asked for the wisdom of the Perl Monks concerning the following question:


Someone passed me a perl script to look at and I quickly realized that I needed to get a test around it. I had never used the Test::More module and I wanted to get some feedback, any tips and some comments.

I watered down the script greatly. Essentially:

$ ./ my-dev-1 --- classes: - all - dev
The script accepts a hostname and spits out a list of classes. Here's the code:
#!/usr/bin/perl use strict; use warnings; use YAML qw( Dump ); use Getopt::Std; use constant { true => 1, false => 0 }; use Data::Dumper; my $deploy = 'common'; my $host = 'unknown'; my $fullhost = 'none'; my @classes = (); my %args = (); getopts( 'hr:', \%args ); sub usage { my $heredoc = <<EOF; Usage: [-h] hostname [ -h ] print this help message EOF print $heredoc; return $heredoc; } # main if (@ARGV == 0) { print "no args\n"; } else { $fullhost = $ARGV[$#ARGV]; $fullhost =~ s/^.*:://; if ( $fullhost =~ /(\w+)-(.*)/ ) { ( $deploy, $host ) = ( $1, $2 ); } } if ( $args{h} ) { usage() } if ( $deploy =~ /^my$/ ) { # Pushing global classes push( @classes, 'all' ); if ( $host =~ /build-/ ) { push( @classes, 'build' ); } # Pushing Dev Classes if ( $host =~ /dev-/ ) { push( @classes, 'dev' ); } } else { push( @classes, 'base' ); } print Dump( { classes => \@classes, } );

So, now I want to wrap some cover and tests around this script. I wrote a little script as a first attempt.

#!/usr/bin/perl use warnings; use strict; use Test::More tests => 2; use Test::Output; require_ok( "./"); is(&usage(), " Usage: [-h] hostname [ -h ] print this help message ", 'check usage message'); done_testing();

Seems to run ok (no pun intended)

$ ./ 1..2 no args --- classes: - base ok 1 - require './'; Usage: [-h] hostname [ -h ] print this help message ok 2 - check usage message

However, now I start to get the feeling that I am doing something wrong. I had to add a return() to the usage function to get that test to pass. Not sure if there is a better way to do that.

I tried the run the code coverage

---------------------------- ------ ------ ------ ------ ------ ------ ------
File                           stmt   bran   cond    sub    pod   time  total
---------------------------- ------ ------ ------ ------ ------ ------ ------                     100.0    n/a    n/a  100.0    n/a    3.1  100.0                       100.0    n/a    n/a  100.0    n/a   96.9  100.0
Total                         100.0    n/a    n/a  100.0    n/a  100.0  100.0
---------------------------- ------ ------ ------ ------ ------ ------ ------

Ok - that really looks wrong. How can I have 100 percent code coverage?

This is where I decided to take a break and do some research and study and make sure I driving in the right direction.

So a couple of questions:

1. Quick review so far - what am missing? Is this the right setup? I understand that a lot of testing in perl works around modules. I just have a script to work with. My goal is to wrap some testing around what I have, and attempt to drive it to something more modular

2. How do I start testing the implied main?

Any thoughts or comments welcomed.

Replies are listed 'Best First'.
Re: Looking for help for unit tests and code coverage on an existing perl script
by kcott (Bishop) on Feb 01, 2014 at 00:55 UTC

    G'day tizatron,

    Given that you're really just testing output from your script, Test::Output seems like a good choice; however, although you've loaded that module, you haven't used any of its functionality.

    When I read "return $heredoc;", I wondered what this was for (it seemed pointless). I do see that you've questioned this yourself: "I had to add a return() to the usage function to get that test to pass ...". If your tests identify logic errors (or similar) in the code you're testing, then do fix the code; however, don't add questionable code just to make the tests pass.

    Here's an example of how you might go about interspersing Test::More and Test::Output tests.

    Sample production script (

    #!/usr/bin/env perl use strict; use warnings; usage() unless @ARGV; print scalar(@ARGV), ": @ARGV\n"; sub usage { warn "Argument required!\n"; exit; }

    Sample test script (pm_script_testing.t):

    #!/usr/bin/env perl use strict; use warnings; use Test::More tests => 4; use Test::Output; stderr_is { qx{perl -c} } " syntax OK\n", 'Test Syntax'; stderr_is { qx{} } "Argument required!\n", 'Test Zero Arguments'; is(qx{ 123}, "1: 123\n", 'Test One Argument'); stdout_is { system qw{ 123 qwe} } "2: 123 qwe\n", 'Test Two Arguments';


    $ pm_script_testing.t 1..4 ok 1 - Test Syntax ok 2 - Test Zero Arguments ok 3 - Test One Argument ok 4 - Test Two Arguments

    If you haven't done so already, you may benefit from reading Test::Tutorial.

    -- Ken


      Your points on Test::Output are well taken. I was experimenting with that module and did get some results via sterr_is and stdout_is.

      The 'is' statement only evaluates a return, so your patterns using Test::Output are much more useful in this context.

      What I really need out of the test suite is code coverage. I pulled down your code and ran the tests. I tried to run something like:

      $ perl -MDevel::Cover $ cover
      I was able to spit out some code coverage numbers. I am going to try spend some time on this path and see I can get it to fly on my test script. But I need to dig in a little more and see if Test::Output aligns with Devel::Cover like I hope it does.
Re: Looking for help for unit tests and code coverage on an existing perl script
by eyepopslikeamosquito (Chancellor) on Feb 01, 2014 at 09:55 UTC

    I would extract a module from your script and unit test the module directly via Test::More and the prove command. I like to keep my script mainlines as short as is practicable, with all the heavy lifting done in (unit-tested) module/s. There are many examples of this general approach on the CPAN; see, for example, the perltidy command, part of the Perl-Tidy distribution and the perlcritic command, part of the Perl-Critic distribution.

    As an alternative, and perhaps a bit less work, you could re-structure your script as a "modulino", that is, a script that can masquerade as a module for ease of testing. This approach is described at:

    See also: How do you test end-user scripts?

      Good links there. Appreciate it.

      In this theme, I went ahead and tried to setup an env similar to the layout described in this link:

      StackOverFlow Complete build/unittest/codecoverage

      couple of things that I did:

      • Created the layout described. Made directories for 'lib' and 't'.
      • Copied my script to lib. Flipped the extension to pm. Added a package statement to the script. Also added: __PACKAGE__->main( @ARGV ) unless caller();
      • Wrapped the main block of code, what I called the implied main, in sub main{...}

      Then I was able to add a stanza to my test file.

      my $my_dev_1 = sample::main("my-dev-1"); is($my_dev_1, "--- classes: - all - dev ", "my dev 1 test");

      Not sure how I feel about the sample::main("my-dev-1"). Would appreciate some feedback on that to see if I am calling this correctly.

      That said, I was able to generate code cover from this setup.

      $ ./Build test
      $ ./Build testcover

      ---------------------------- ------ ------ ------ ------ ------ ------ ------
      File                           stmt   bran   cond    sub    pod   time  total
      ---------------------------- ------ ------ ------ ------ ------ ------ ------
      blib/lib/             97.4   91.7    n/a  100.0    0.0  100.0   93.2
      Total                          97.4   91.7    n/a  100.0    0.0  100.0   93.2
      ---------------------------- ------ ------ ------ ------ ------ ------ ------

      That processes pumps out a cover.html file that kinda aligns more with what I was hoping to see. The changes to the original code are not significant, but they are changes, more than what I was hoping to make, perhaps digging in harder on Test::Output would help.

Re: Looking for help for unit tests and code coverage on an existing perl script
by dasgar (Priest) on Feb 01, 2014 at 00:25 UTC

    I can't offer suggestions/tips on testing. Haven't gotten into using tests like I probably should.

    As for trying to figure out your test coverage, you may want to check out Devel::Cover.