Devel::Cover(3pm) User Contributed Perl Documentation Devel::Cover(3pm)
NAME
Devel::Cover - Code coverage metrics for Perl
VERSION
version 0.89
SYNOPSIS
To get coverage for an uninstalled module:
cover -test
or
cover -delete
HARNESS_PERL_SWITCHES=-MDevel::Cover make test
cover
To get coverage for an uninstalled module which uses Module::Build (0.26 or later):
./Build testcover
If the module does not use the t/*.t framework:
PERL5OPT=-MDevel::Cover make test
If you want to get coverage for a program:
perl -MDevel::Cover yourprog args
cover
perl -MDevel::Cover=-db,cover_db,-coverage,statement,time yourprog args
DESCRIPTION
This module provides code coverage metrics for Perl. Code coverage metrics describe how thoroughly tests exercise code. By using
Devel::Cover you can discover areas of code not exercised by your tests and determine which tests to create to increase coverage. Code
coverage can be considered as an indirect measure of quality.
Although it is still being developed, Devel::Cover is now quite stable and provides many of the features to be expected in a useful
coverage tool.
Statement, branch, condition, subroutine, and pod coverage information is reported. Statement coverage data should be reasonable. Branch
and condition coverage data should be mostly accurate too, although not always what one might initially expect. Subroutine coverage should
be as accurate as statement coverage. Pod coverage comes from Pod::Coverage. If Pod::Coverage::CountParents is available it will be used
instead. Coverage data for other criteria are not yet collected.
The cover program can be used to generate coverage reports. Devel::Cover ships with a number of different reports including various types
of HTML output, textual reports, a report to display missing coverage in the same format as compilation errors and a report to display
coverage information within the Vim editor.
It is possible to add annotations to reports, for example you could add a column to an HTML report showing who last changed a line, as
determined by git blame. Some annotation modules are shipped with Devel::Cover and you can easily create your own.
The gcov2perl program can be used to convert gcov files to "Devel::Cover" databases. This allows you to display your C or XS code coverage
together with your Perl coverage, or to use any of the Devel::Cvoer reports to display your C coverage data.
You may find that the coverage results don't match your expectations. This could be due to a bug in Devel::Cover, but code coverage can be
unintuitive to newcomers, and especially so with Perl, so you may want to reconsider your expectations as well.
Code coverage data are collected by replacing perl ops with functions which count how many times the ops are executed. These data are then
mapped back to reality using the B compiler modules. There is also a statement profiling facility which should not be relied on. For
proper profiling use Devel::NYTProf. Previous versions of Devel::Cover collected coverage data by replacing perl's runops function. It is
still possible to switch to that mode of operation, but this now gets little testing and will probably be removed soon. You probably don't
care about any of this.
The most appropriate mailing list on which to discuss this module would be perl-qa. Discussion has migrated there from perl-qa-metrics
which is now defunct. See http://lists.perl.org/list/perl-qa.html <http://lists.perl.org/list/perl-qa.html>.
The Devel::Cover repository can be found at http://github.com/pjcj/Devel--Cover <http://github.com/pjcj/Devel--Cover>.
REQUIREMENTS AND RECOMMENDED MODULES
REQUIREMENTS
o Perl 5.6.1 or greater. Perl 5.8.8 or greater is recommended.
Perl 5.7 is unsupported. Perl 5.8.8 or greater is recommended. Perl 5.8.7 has problems and may crash. Whilst Perl 5.6 should mostly
work you will probably miss out on coverage information which would be available using a more modern version and will likely run into
bugs in perl. Different versions of perl may give slightly different results due to changes in the op tree.
o The ability to compile XS extensions.
This means a working C compiler and make program at least. If you built perl from source you will have these already and they will be
used automatically. If your perl was built in some other way, for example you may have installed it using your Operating System's
packaging mechanism, you will need to ensure that the appropriate tools are installed.
o Storable and Digest::MD5
Both are in the core in Perl 5.8.0 and above.
OPTIONAL MODULES
o Template, and either PPI::HTML or Perl::Tidy
Needed if you want syntax highlighted HTML reports.
o Pod::Coverage (0.06 or above) or Pod::Coverage::CountParents
One is needed if you want Pod coverage. If Pod::Coverage::CountParents is installed, it is preferred.
o Test::More
Required if you want to run Devel::Cover's own tests.
o Test::Warn
Some of Devel::Cover's own tests require it.
o Test::Differences
if the tests fail and you would like nice output telling you why.
o Template, and Parallel::Iterator
Needed if you want to run cpancover.
Use with mod_perl
By adding "use Devel::Cover;" to your mod_perl startup script, you should be able to collect coverage information when running under
mod_perl. You can also add any options you need at this point. I would suggest adding this as early as possible in your startup script in
order to collect as much coverage information as possible.
OPTIONS
-blib - "use blib" and ignore files matching t/ (default true
iff blib directory exists).
-coverage criterion - Turn on coverage for the specified criterion. Criteria
include statement, branch, condition, path, subroutine,
pod, time, all and none (default all available).
-db cover_db - Store results in coverage db (default ./cover_db).
-dir path - Directory in which coverage will be collected (default
cwd).
-ignore RE - Set REs of files to ignore (default "/Devel/Cover").
+ignore RE - Append to REs of files to ignore.
-inc path - Set prefixes of files to ignore (default @INC).
+inc path - Append to prefixes of files to ignore.
-merge val - Merge databases, for multiple test benches (default on).
-select RE - Set REs of files to select (default none).
+select RE - Append to REs of files to select.
-silent val - Don't print informational messages (default off).
-subs_only val - Only cover code in subroutine bodies (default off).
-replace_ops val - Use op replacing rather than runops (default on).
-summary val - Print summary information iff val is true (default on).
More on Coverage Options
You can specify options to some coverage criteria. At the moment only pod coverage takes any options. These are the parameters which are
passed into the Pod::Coverage constructor. The extra options are separated by dashes, and you may specify as many as you wish. For
example, to specify that all subroutines containing xx are private, call Devel::Cover with the option -coverage,pod-also_private-xx.
SELECTING FILES TO COVER
You may select the files for which you want to collect coverage data using the select, ignore and inc options. The system uses the
following procedure to decide whether a file will be included in coverage reports:
o If the file matches a RE given as a select option, it will be included.
o Otherwise, if it matches a RE given as an ignore option, it won't be included.
o Otherwise, if it is in one of the inc directories, it won't be included.
o Otherwise, it will be included.
You may add to the REs to select by using +select, or you may reset the selections using -select. The same principle applies to the REs to
ignore.
The inc directories are initially populated with the contents of the @INC array at the time Devel::Cover was built. You may reset these
directories using -inc, or add to them using +inc.
Although these options take regular expressions, you should not enclose the RE within // or any other quoting characters.
ENVIRONMENT
The -silent option is turned on when Devel::Cover is invoked via $HARNESS_PERL_SWITCHES or $PERL5OPT. Devel::Cover tries to do the right
thing when $MOD_PERL is set. $DEVEL_COVER_OPTIONS is appended to any options passed into Devel::Cover.
When running Devel::Cover's own test suite, $DEVEL_COVER_DEBUG turns on debugging information, $DEVEL_COVER_GOLDEN_VERSION overrides
Devel::Cover's own idea of which golden results it should test against, and $DEVEL_COVER_NO_COVERAGE runs the tests without collecting
coverage. The environment variables described in this paragraph are of interest to Devel::Cover maintainers only.
ACKNOWLEDGEMENTS
Some code and ideas cribbed from:
Devel::OpProf
B::Concise
B::Deparse
SEE ALSO
Devel::Cover::Tutorial
B
Pod::Coverage
LIMITATIONS
There are things that Devel::Cover can't cover.
Absence of shared dependencies
Perl keeps track of which modules have been loaded (to avoid reloading them). Because of this, it isn't possible to get coverage for a
path where a runtime import fails if the module being imported is one that Devel::Cover uses internally. For example, suppose your program
has this function:
sub foo {
eval { require Storable };
if ($@) {
carp "Can't find Storable";
return;
}
# ...
}
You might write a test for the failure mode as
BEGIN { @INC = () }
foo();
# check for error message
Because Devel::Cover uses Storable internally, the import will succeed (and the test will fail) under a coverage run.
Modules used by Devel::Cover while gathering coverage:
o B
o B::Debug
o B::Deparse
o Carp
o Cwd
o Digest::MD5
o File::Path
o File::Spec
o Storable
Redefined subroutines
If you redefine a subroutine you may find that the original subroutine is not reported on. This is because I haven't yet found a way to
locate the original CV. Hints, tips or patches to resolve this will be gladly accepted.
BUGS
Almost certainly.
See the BUGS file, the TODO file and the bug trackers at https://rt.cpan.org/Public/Dist/Display.html?Name=Devel-Cover and
https://github.com/pjcj/Devel--Cover/issues?sort=created&direction=desc&state=open
LICENCE
Copyright 2001-2012, Paul Johnson (paul@pjcj.net)
This software is free. It is licensed under the same terms as Perl itself.
The latest version of this software should be available on CPAN and from my homepage: http://www.pjcj.net/.
perl v5.14.2 2012-06-15 Devel::Cover(3pm)