(I reported this on perl.qa a week ago but, surprisingly, have not elicited a single response. So please excuse the double-post.)

I have encountered an anomaly in my use of Devel::Cover.

Suppose that I have two packages, Alpha and Beta, each of which implements a sayhowdy() method, albeit slightly differently from each other. 

   # in Alpha.pm

   sub sayhowdy {
     my $self = shift;
     my $string = q{};
     open my $fh, ">", \$string;
     print $fh "Howdy, alpha\n";
     close $fh;
     return $string;
   }

   # in Beta.pm

   sub sayhowdy {
     my $self = shift;
     my $string = q{};
     open my $fh, ">", \$string;
     print $fh "Howdy, beta\n";
     close $fh;
     return $string;
   }

[download]

(You can play along at home by downloading this tarball.)

The only other non-trivial difference between the two packages is that the final statement in Beta.pm assigns Beta::sayhowdy() to Alpha::sayhowdy() should Alpha::sayhowdy() somehow be (or get) undefined. 

   *Alpha::sayhowdy = \&sayhowdy if ! defined &Alpha::sayhowdy;

[download]

I can write the following test file to demonstrate that this reassignment can actually be made: 

   use Test::More qw( no_plan);

   use_ok( q{Alpha} );

   my $class = q{Alpha};
   my $self = $class->new();

   isa_ok($self, $class);
   can_ok($class, q{sayhowdy} );

   is($self->sayhowdy(), qq{Howdy, alpha\n},
       "alpha sayhowdy okay");

   undef &Alpha::sayhowdy;
   eval { $self->sayhowdy(); };
   like($@, qr/^Undefined subroutine &Alpha::sayhowdy called/,
       "Alpha::sayhowdy() is now undefined");


   require_ok('Beta');
   is($self->sayhowdy(), qq{Howdy, beta\n},
       "Beta::sayhowdy is now Alpha::sayhowdy");

[download]

... which produces: 

   [Alpha] 539 $ prove -vb t/03_gamma.t
   t/03_gamma....ok 1 - use Alpha;
   ok 2 - The object isa Alpha
   ok 3 - Alpha->can('sayhowdy')
   ok 4 - alpha sayhowdy okay
   ok 5 - Alpha::sayhowdy() is now undefined
   ok 6 - require Beta;
   ok 7 - Beta::sayhowdy is now Alpha::sayhowdy
   1..7
   ok
   All tests successful.
   Files=1, Tests=7,  0 wallclock secs

[download]

So far, so good. But when I run Devel::Cover on this distribution, the coverage report treats the glob assignment line above as if it weren't even there. 

   $ cover -delete
   $ make test HARNESS_PERL_SWITCHES=1
   $ cover cover_db --report=txt > coverage.txt

   # in the section of coverage.txt reporting on lib/Beta.pm:
   # (for simplicity, displaying only statement coverage)

   blib/lib/Beta.pm

   line  err   stmt   code
   1                  package Beta;
   2                  #$Id#
   3              2   use strict;

   # [snip]

   16             2       print $fh "Howdy, beta\n";
   17             2       close $fh;
   18             2       return $string;
   19                 }
   20
   21                 *Alpha::sayhowdy = \&sayhowdy
                          if ! defined &Alpha::sayhowdy;
   22
   23                 1;

[download]

The test file above clearly exercises line 21, but Devel::Cover reports nothing at all about that line. Has anyone encountered/can anyone explain this?

Thanks in advance.

Jim Keenan

In reply to Devel::Cover failing to report on tested statement by jkeenan1

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