1Devel::Cover(3) User Contributed Perl Documentation Devel::Cover(3)
2
6 Devel::Cover - Code coverage metrics for Perl
7
9 To get coverage for an uninstalled module:
10 cover -test
12 or
14 cover -delete
16 HARNESS_PERL_SWITCHES=-MDevel::Cover make test
17 cover
18 To get coverage for an uninstalled module which uses Module::Build
20 (0.26 or later):
21 ./Build testcover
23 If the module does not use the t/*.t framework:
25 PERL5OPT=-MDevel::Cover make test
27 If you want to get coverage for a program:
29 perl -MDevel::Cover yourprog args
31 cover
32 perl -MDevel::Cover=-db,cover_db,-coverage,statement,time yourprog args
34
36 This module provides code coverage metrics for Perl. Code coverage
37 metrics describe how thoroughly tests exercise code. By using
38 Devel::Cover you can discover areas of code not exercised by your tests
39 and determine which tests to create to increase coverage. Code coverage
40 can be considered as an indirect measure of quality.
41 I consider this software to have an alpha status. By that I mean that
43 I reserve the right to alter the interface in a backwards incompatible
44 manner without incrementing the major version number. I specifically
45 do not mean that this software is full of bugs or missing key features.
46 Although I'm making no guarantees on that front either. In short, if
47 you are looking for code coverage software for Perl, you have probably
48 come to the end of your search. For more of my opinions on this
49 subject, see http://pjcj.sytes.net/notes/2007/03/14#alpha
50 Code coverage data are collected using a pluggable runops function
52 which counts how many times each op is executed. These data are then
53 mapped back to reality using the B compiler modules. There is also a
54 statement profiling facility which needs a better backend to be really
55 useful. This release also includes an experimental mode which replaces
56 ops instead of using a pluggable runops function. This provides a nice
57 speed increase, but needs better testing before it becomes the default.
58 You probably don't care about any of this.
59 The cover program can be used to generate coverage reports.
61 Statement, branch, condition, subroutine, pod and time coverage
63 information is reported. Statement coverage data should be reasonable,
64 although there may be some statements which are not reported. Branch
65 and condition coverage data should be mostly accurate too, although not
66 always what one might initially expect. Subroutine coverage should be
67 as accurate as statement coverage. Pod coverage comes from
68 Pod::Coverage. If Pod::Coverage::CountParents is available it will be
69 used instead. Coverage data for path coverage are not yet collected.
70 The gcov2perl program can be used to convert gcov files to
72 "Devel::Cover" databases.
73 You may find that the results don't match your expectations. I would
75 imagine that at least one of them is wrong.
76 The most appropriate mailing list on which to discuss this module would
78 be perl-qa. Discussion has migrated there from perl-qa-metrics which
79 is now defunct. See <http://lists.perl.org/showlist.cgi?name=perl-qa>.
80
82 · Perl 5.6.1 or greater. Perl 5.8.2 or greater is recommended.
83 Perl 5.7.0 is unsupported. Perl 5.8.2 or greater is recommended.
85 Whilst Perl 5.6 should mostly work you will probably miss out on
86 coverage information which would be available using a more modern
87 version and will likely run into bugs in perl. Perl 5.8.0 will
88 give slightly different results to more recent versions due to
89 changes in the op tree.
90 · The ability to compile XS extensions.
92 This means a working compiler and make program at least.
94 · Storable and Digest::MD5
96 Both are in the core in Perl 5.8.0 and above.
98 · Template and PPI::HTML or Perl::Tidy
100 if you want syntax highlighted HTML reports.
102 · Pod::Coverage
104 if you want Pod coverage.
106 · Test::Differences
108 if the tests fail and you would like nice output telling you why.
110
112 -blib - "use blib" and ignore files matching \bt/ (default true
113 iff blib directory exists).
114 -coverage criterion - Turn on coverage for the specified criterion. Criteria
115 include statement, branch, condition, path, subroutine,
116 pod, time, all and none (default all available).
117 -db cover_db - Store results in coverage db (default ./cover_db).
118 -dir path - Directory in which coverage will be collected (default
119 cwd).
120 -ignore RE - Set REs of files to ignore (default "/Devel/Cover\b").
121 +ignore RE - Append to REs of files to ignore.
122 -inc path - Set prefixes of files to ignore (default @INC).
123 +inc path - Append to prefixes of files to ignore.
124 -merge val - Merge databases, for multiple test benches (default on).
125 -select RE - Set REs of files to select (default none).
126 +select RE - Append to REs of files to select.
127 -silent val - Don't print informational messages (default off)
128 -subs_only val - Only cover code in subroutine bodies (default off)
129 -summary val - Print summary information iff val is true (default on).
130 More on Coverage Options
132 You can specify options to some coverage criteria. At the moment only
133 pod coverage takes any options. These are the parameters which are
134 passed into the Pod::Coverage constructor. The extra options are
135 separated by dashes, and you may specify as many as you wish. For
136 example, to specify that all subroutines containing xx are private,
137 call Devel::Cover with the option -coverage,pod-also_private-xx.
138
140 You may select which files you want covered using the select, ignore
141 and inc options. The system works as follows:
142 Any file matching a RE given as a select option is selected.
144 Otherwise, any file matching a RE given as an ignore option is ignored.
146 Otherwise, any file in one of the inc directories is ignored.
148 Otherwise the file is selected.
150 You may add to the REs to select by using +select, or you may reset the
152 selections using -select. The same principle applies to the REs to
153 ignore.
154 The inc directories are initially populated with the contents of the
156 @INC array at the time Devel::Cover was built. You may reset these
157 directories using -inc, or add to them using +inc.
158 Although these options take regular expressions, you should not enclose
160 the RE within // or any other quoting characters.
161
163 The -silent option is turned on when Devel::Cover is invoked via
164 $HARNESS_PERL_SWITCHES or $PERL5OPT. Devel::Cover tries to do the
165 right thing when $MOD_PERL is set. $DEVEL_COVER_OPTIONS is appended to
166 any options passed into Devel::Cover.
167 When running Devel::Cover's own test suite, $DEVEL_COVER_DEBUG turns on
169 debugging information, $DEVEL_COVER_GOLDEN_VERSION overrides
170 Devel::Cover's own idea of which golden results it should test against,
171 and $DEVEL_COVER_NO_COVERAGE runs the tests without collecting
172 coverage.
173
175 Some code and ideas cribbed from:
176 Devel::OpProf
178 B::Concise
179 B::Deparse
180
182 Devel::Cover::Tutorial
183 B
184 Pod::Coverage
185
187 There are things that Devel::Cover can't cover.
188 Absence of shared dependencies
190 Perl keeps track of which modules have been loaded (to avoid reloading
191 them). Because of this, it isn't possible to get coverage for a path
192 where a runtime import fails if the module being imported is one that
193 Devel::Cover uses internally. For example, suppose your program has
194 this function:
195 sub foo {
197 eval { require Storable };
198 if ($@) {
199 carp "Can't find Storable";
200 return;
201 }
202 # ...
203 }
204 You might write a test for the failure mode as
206 BEGIN { @INC = () }
208 foo();
209 # check for error message
210 Because Devel::Cover uses Storable internally, the import will succeed
212 (and the test will fail) under a coverage run.
213 Modules used by Devel::Cover while gathering coverage:
215 · B
217 · B::Debug
219 · B::Deparse
221 · Carp
223 · Cwd
225 · Digest::MD5
227 · File::Path
229 · File::Spec
231 · Storable
233 mod_perl
235 By adding "use Devel::Cover;" to your mod_perl startup script, you
236 should be able to collect coverage information when running under
237 mod_perl. You can also add any options you need at this point. I
238 would suggest adding this as early as possible in your startup script
239 in order to collect as much coverage information as possible.
240 Redefined subroutines
242 If you redefine a subroutine you may find that the original subroutine
243 is not reported on. This is because I haven't yet found a way to
244 locate the original CV. Hints, tips or patches to resolve this will be
245 gladly accepted.
246
248 Almost certainly.
249 See the BUGS file. And the TODO file.
251
253 Version 0.65 - 8th August 2009
254
256 Copyright 2001-2009, Paul Johnson (pjcj@cpan.org)
257 This software is free. It is licensed under the same terms as Perl
259 itself.
260 The latest version of this software should be available from my
262 homepage: http://www.pjcj.net
263perl v5.10.1 2009-08-08 Devel::Cover(3)