NAME
Test::Warnings - Test for warnings and the lack of them
VERSION
version 0.014
SYNOPSIS
use Test::More;
use Test::Warnings;
pass('yay!');
done_testing;
emits TAP:
ok 1 - yay!
ok 2 - no (unexpected) warnings (via done_testing)
1..2
and:
use Test::More tests => 3;
use Test::Warnings 0.005 ':all';
pass('yay!');
like(warning { warn "oh noes!" }, qr/^oh noes/, 'we warned');
emits TAP:
ok 1 - yay!
ok 2 - we warned
ok 3 - no (unexpected) warnings (via END block)
1..3
DESCRIPTION
If you've ever tried to use Test::NoWarnings to confirm there are no warnings
generated by your tests, combined with the convenience of done_testing
to
not have to declare a
test count,
you'll have discovered that these two features do not play well together,
as the test count will be calculated before the warnings test is run,
resulting in a TAP error. (See examples/test_nowarnings.pl
in this
distribution for a demonstration.)
This module is intended to be used as a drop-in replacement for
Test::NoWarnings: it also adds an extra test, but runs this test before
done_testing
calculates the test count, rather than after. It does this by
hooking into done_testing
as well as via an END
block. You can declare
a plan, or not, and things will still Just Work.
It is actually equivalent to:
use Test::NoWarnings 1.04 ':early';
as warnings are still printed normally as they occur. You are safe, and
enthusiastically encouraged, to perform a global search-replace of the above
with use Test::Warnings;
whether or not your tests have a plan.
It can also be used as a replacement for Test::Warn, if you wish to test the content of expected warnings; read on to find out how.
FUNCTIONS
The following functions are available for import (not included by default; you
can also get all of them by importing the tag :all
):
allow_warnings([bool])
- EXPERIMENTAL - MAY BE REMOVED
When passed a true value, or no value at all, subsequent warnings will not
result in a test failure; when passed a false value, subsequent warnings will
result in a test failure. Initial value is false
.
When warnings are allowed, any warnings will instead be emitted via Test::Builder::note.
allowing_warnings
- EXPERIMENTAL - MAY BE REMOVED
Returns whether we are currently allowing warnings (set by allow_warnings
as described above).
had_no_warnings(<optional test name>)
Tests whether there have been any warnings so far, not preceded by an
allowing_warnings
call. It is run
automatically at the end of all tests, but can also be called manually at any
time, as often as desired.
warnings( { code } )
Given a code block, runs the block and returns a list of all the
(not previously allowed via allow_warnings
) warnings issued within. This
lets you test for the presence of warnings that you not only would allow,
but must be issued. Testing functions are not provided; given the strings
returned, you can test these yourself using your favourite testing functions,
such as Test::More::is or Test::Deep::cmp_deeply.
Warnings generated by this code block are NOT propagated further. However,
since they are returned from this function with their filename and line
numbers intact, you can re-issue them yourself immediately after calling
warnings(...)
, if desired.
warning( { code } )
Same as warnings( { code } )
, except a scalar is always returned - the
single warning produced, if there was one, or an arrayref otherwise -- which
can be more convenient to use than warnings()
if you are expecting exactly
one warning.
However, you are advised to capture the result from warning()
into a temp
variable so you can dump its value if it doesn't contain what you expect.
e.g. with this test:
like(
warning { foo() },
qr/^this is a warning/,
'got a warning from foo()',
);
if you get two warnings (or none) back instead of one, you'll get an arrayref, which will result in an unhelpful test failure message like:
# Failed test 'got a warning from foo()'
# at t/mytest.t line 10.
# 'ARRAY(0xdeadbeef)'
# doesn't match '(?^:^this is a warning)'
So instead, change your test to:
my $warning = warning { foo() };
like(
$warning,
qr/^this is a warning/,
'got a warning from foo()',
) or diag 'got warning(s): ', explain($warning);
IMPORT OPTIONS
:all
- Imports all functions listed above:no_end_test
- Disables the addition of ahad_no_warnings
test viaEND
ordone_testing
CAVEATS
Sometimes new warnings can appear in Perl that should not block installation -- for example, smartmatch was recently deprecated in perl 5.17.11, so now any distribution that uses smartmatch and also tests for warnings cannot be installed under 5.18.0. You might want to consider only making warnings fail tests in an author environment -- you can do this with the if pragma:
use if $ENV{AUTHOR_TESTING} || $ENV{RELEASE_TESTING}, 'Test::Warnings';
In future versions of this module, when interfaces are added to test the
content of warnings, there will likely be additional sugar available to
indicate that warnings should be checked only in author tests (or TODO when
not in author testing), but will still provide exported subs. Comments are
enthusiastically solicited - drop me an email, write up an RT ticket, or come
by #perl-qa
on irc!
Achtung! This is not a great idea:
sub warning_like(&$;$) {
my ($code, $pattern, $name) = @_;
like( &warning($code), $pattern, $name );
}
warning_like( { ... }, qr/foo/, 'foo appears in the warning' );
If the code in the { ... }
is going to warn with a stack trace with the
arguments to each subroutine in its call stack (for example via Carp::cluck
),
the test name, "foo appears in the warning" will itself be matched by the
regex. Instead, write this:
like( warning { ... }, qr/foo/, 'foo appears in the warning' );
TO DO (or: POSSIBLE FEATURES COMING IN FUTURE RELEASES)
allow_warnings(qr/.../)
- allow some warnings and not others- more sophisticated handling in subtests - if we save some state on the
Test::Builder object itself, we can allow warnings in a subtest and then
the state will revert when the subtest ends, as well as check for warnings at
the end of every subtest via
done_testing
. - sugar for making failures TODO when testing outside an author environment
SUPPORT
Bugs may be submitted through https://rt.cpan.org/Public/Dist/Display.html?Name=Test-Warnings.
I am also usually active on irc, as 'ether' at irc.perl.org
.
SEE ALSO
- Test::NoWarnings
- Test::FailWarnings
- blogs.perl.org: YANWT (Yet Another No-Warnings Tester)
strictures - which makes all warnings fatal in tests, hence lessening
the need for special warning testing
- Test::Fatal
AUTHOR
Karen Etheridge ether@cpan.org
COPYRIGHT AND LICENSE
This software is copyright (c) 2013 by Karen Etheridge.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.
CONTRIBUTORS
- Graham Knop haarg@haarg.org
- Leon Timmermans fawaka@gmail.com