Advanced use of Devel::Cover

Braga, Portugal -- 1st September 2005

Paul Johnson

www.pjcj.net

Devel::Cover

• Aimed at those who have used Devel::Cover
• or at least been to the introductory talk
• How to be more productive using Devel::Cover

Integration into the build process

• Using Devel::Cover should be easy
• in fact, everything should be easy
• Automate it!

ExtUtils::MakeMaker

$ cover -test

ExtUtils::MakeMaker

sub MY::postamble
{
    qq[
testcover :
\t cover -test
    ]
}

ExtUtils::MakeMaker

sub MY::postamble
{
    qq[
testcover :
\t cover -delete && \\
   HARNESS_PERL_SWITCHES=-MDevel::Cover \$(MAKE) test && \\
   cover -report text
    ]
}

ExtUtils::MakeMaker

use ExtUtils::MakeMaker::Coverage;

Written by Steve Peters

Module::Build

$ ./Build testcover

$ DEVEL_COVER_OPTIONS=-ignore,Build ./Build testcover

File Selection

• Collecting coverage data is expensive
• So don't collect more than necessary
• Pass options into Devel::Cover
• -select
• -ignore
• -inc

File Selection

• These are regular expressions
• Any file that is selected is selected
• otherwise any file that is ignored is ignored
• otherwise any file in one of the inc directories is ignored
• otherwise the file is selected

File Selection

• Add to the REs to select by using +select
• Reset the selections using -select
• The same principle applies to the REs to ignore
• inc directories are populated by @INC at the time Devel::Cover is built
• +inc adds to the list, -inc resets it
• defaults for ignore if blib exists: '^t/', '\.t', '^test\.pl'
• -MDevel::Cover=-select,Mylib,+ignore,fools

Covering mod_perl

• Use Apache::Test
• make testcover
• Read the docs

Covering XS code

• C code coverage tool required
• For example, gcov
• CCFLAGS=-fprofile-arcs\ -ftest-coverage
• OTHERLDFLAGS=-fprofile-arcs\ -ftest-coverage
• $ make testcover
• $ gcov Mylib.xs
• $ gcov2perl Mylib.xs.gcov
• $ cover

Covering XS code

• Let the train take the strain
• $ cover -test

Increasing Coverage

• Write more tests
• Remove unused code
• Merge databases from different runs

Merging Databases

• Database is normally cover_db directory and contents
• Parts stored using Storable
• Uses nstore for portability
• Run tests on different platforms
• Use NFS or copy the directories somehow
• $ cover db1 db2 db3

Error Conditions

• open F, ">", \$file or die "Cannot open $file: $!"
• close F or die "Cannot close $file: $!"

Error Conditions

• Is it worth checking those error conditions?
• BEGIN { *CORE::GLOBAL::close = sub { 0 } }
• { local *Mylib::meth = sub { 0 }; tst }

Uncoverable code

• What if it is impossible to test some code?
• $x = shift || 7;
• sub def { 1 } $x = shift || def;
• In general, Devel::Cover can't know that a sub always returns true
• Some people will rewrite the construct
• Pah! It's a bug in Devel::Cover!
• Tell Devel::Cover what code is uncovered

Uncoverable code

• Currently in development
• Principles tested
• Uses .uncoverable file
• md5sum of text on line
• People seem keen on comments in code
• Fixing up html report

Annotations

• Sometimes viewing other information can be useful
• Who last changed the untested code?
• Write an annotation!
• Currently available for svk
• Use the API

Reports

• Still not satisfied?
• Write a report!
• Please!
• CGI or mod_perl
• AJAX
• Tk, GTK+, wx
• curses
• Use the API

Problems Opportunities

• Threads
• Not running END blocks
• eval "use $mod" if int rand 2;
• ... and many more ...

Future

• TODO
• Optimal test ordering and redundancy checking
• Mutation Coverage