| Test::Trap - Trap exit codes, exceptions, output, etc. |
Test::Trap - Trap exit codes, exceptions, output, etc.
Version 0.3.2
use Test::More; use Test::Trap;
my @r = trap { some_code(@some_parameters) };
is ( $trap->exit, 1, 'Expecting &some_code to exit with 1' );
is ( $trap->stdout, '', 'Expecting no STDOUT' );
like ( $trap->stderr, qr/^Bad parameters; exiting\b/, 'Expecting warnings.' );
Primarily (but not exclusively) for use in test scripts: A block eval on steroids, configurable and extensible, but by default trapping (Perl) STDOUT, STDERR, warnings, exceptions, would-be exit codes, and return values from boxed blocks of test code.
The values collected by the latest trap can then be queried or tested through a special trap object.
A function and a scalar may be exported by any name. The function (by
default named trap) is an analogue to block eval(), and the scalar
(by default named $trap) is the corresponding analogue to $@.
Optionally, you may specify the layers of the exported trap. Layers
may be specified by name, with a colon sigil. Multiple layers may be
given in a list, or just stringed together like :flow:stderr:warn.
(For the advanced user, you may also specify anonymous layer implementations -- i.e. an appropriate subroutine.)
See below for a list of the built-in layers, most of which are enabled by default. Note, finally, that the ordering of the layers matter: The :raw layer is always on the bottom (anything underneath it is ignored), and any other ``flow control'' layers used should be right down there with it.
This function may be exported by any name, but defaults to trap.
By default, traps exceptions (like block eval), but also exits and
exit codes, returns and return values, context, and (Perl) output on
STDOUT or STDERR, and warnings. All information trapped can be
queried through the trap object, which is by default exported as
$trap, but can be exported by any name.
The value returned from trap mimics that returned from eval: If
the BLOCK would die or exit, it returns an undefined value in
scalar context or an empty list in list context; otherwise it returns
whatever the BLOCK would return in the given context (also
available as the trapped return values).
Exactly what the trap traps depends on the layers of the trap. It
is possible to register more (see the Test::Trap::Builder manpage), but the
following layers are pre-defined by this module:
The only built-in terminating layer, at which the processing of the
layers stops, and the actual call to the user code is performed. On
success, it collects the return value(s) in the appropriate context.
Pushing the :raw layer on a trap will for most purposes remove all
layers below.
The layer emulating block eval, trapping normal exceptions.
The third ``flow control'' layer, capturing exit codes if anything used in the dynamic scope of the trap calls CORE::GLOBAL::exit(). (See CAVEATS below for more.)
A shortcut for :raw:die:exit (effectively pushing all three layers on the trap). Since this includes :raw, it is also terminating: Pushing :flow on a trap will effectively remove all layers below.
Layers trapping Perl output on STDOUT and STDERR, respectively.
As above, but specifying a capture strategy using PerlIO::scalar. If this strategy is not available (typically if PerlIO is not), this is an error. See CAPTURE STRATEGIES.
As above, but specifying a capture strategy using File::Temp. Note
that this is the default strategy, unless the :output() layer is
used to set another default. See CAPTURE STRATEGIES.
(Either syntax, commas or semicolons, is permitted, as is any number of names in the list.) As above, but specifying the capture strategy by the first existing name among a, b, and c. If no such strategy is found, this is an error. See CAPTURE STRATEGIES.
A layer trapping warnings, with additional tee: If STDERR is open, it will also print the warnings there. (This output may be trapped by the :stderr layer, be it above or below the :warn layer.)
A short-cut for :raw:die:exit:stdout:stderr:warn (effectively pushing all six layers on the trap). Since this includes :raw, it is also terminating: Pushing :default on a trap will effectively remove all layers below.
The other interesting property of :default is that it is what every trap starts with: In order not to include the six layers that make up :default, you need to push a terminating layer (such as :raw or :flow) on the trap.
A (non-default, non-trapping) layer that installs a callback method (by name) m to be run on test failures. To run the diag_all method every time a test fails:
use Test::Trap qw/ :on_fail(diag_all) /;
These (non-default, non-trapping) layers will cause the trapped user code to be run in void, scalar, or list context, respectively. (By default, the trap will propagate context, that is, it will run the code in whatever context the trap itself is in.)
If more than one of these layers are pushed on the trap, the deepest (that is, leftmost) takes precedence:
use Test::Trap qw/ :scalar:void:list /;
trap { 42, 13 };
$trap->return_is_deeply( [ 13 ], 'Scalar comma.' );
A (non-default, non-trapping) layer that sets the default capture
strategy for any output trapping (:stdout, :stderr, or other
similarly defined) layers below iton the trap.
use Test::Trap qw/ :output(systemsafe) /;
trap { system echo => 'Hello Unix!' }; # trapped!
use Test::Trap qw/ :flow:stderr:output(systemsafe):stdout /;
trap { system echo => 'Hello Unix!' }; # *not* trapped!
trap { system q/ echo 'Hello Unix!' >&2 / }; # trapped!
See CAPTURE STRATEGIES.
How output is trapped, depends on the capture strategy used. It is possible to register more (see the Test::Trap::Builder manpage), but the following strategies are pre-defined by this module:
The default capture strategy, provided by the Test::Trap::Builder::TempFile manpage, in which output is temporarily redirected to (and read back from) a tempfile.
A variant of the capture strategy provided by the Test::Trap::Builder::TempFile manpage, in which the handles used to write to and read from the tempfile are both binmoded with the same perlio layers as the trapped output handle originally had.
Caveat emptor: If the handle has perlio custom layers, they may (or may not) fail to apply to the tempfile read and write handles.
A capture strategy provided by the Test::Trap::Builder::SystemSafe manpage, like the default strategy, except it outputs on file handles with the same file descriptors as the trapped output handle originally had, and so can be used to trap output from forked-off processes, including system().
This strategy may be ``safe'' in relation to forked-off processes, but it is fragile. For one, it only works with handles that have ``real'' file descriptors. For another, it depends on the original file descriptors being available after closing. (If signal handlers or threads open files, they may well not be.) And it may fail in other ways. But in relation to forked-off processes, the other pre-defined strategies will silently fail to trap, as will similarly simple strategies. This one, when not crashing, will trap that output.
A variant of the capture strategy provided by the Test::Trap::Builder::SystemSafe manpage, in which the handles used to write to and read from the tempfile are both binmoded with the same perlio layers as the trapped output handle originally had.
Caveat emptor: If the handle has perlio custom layers, they may (or may not) fail to apply to the tempfile read and write handles.
A capture strategy provided by the Test::Trap::Builder::PerlIO manpage, in which output is temporarily redirected to an in-memory file via PerlIO::scalar.
If PerlIO::scalar is not available, neither is this strategy.
The following methods may be called on the trap objects after any trap has been sprung, and access the outcome of the run.
Any property will be undef if not actually trapped -- whether because there is no layer to trap them or because flow control passed them by. (If there is an active and successful trap layer, empty strings and empty arrays trapped will of course be defined.)
When properties are set, their values will be as follows:
A string indicating how the trap terminated: return, die, or
exit.
The exception, if the latest trap threw one.
The exit code, if the latest trap tried to exit (by way of the trap's own &CORE::GLOBAL::exit only; see CAVEATS).
Returns undef if the latest trap did not terminate with a return; otherwise returns three different views of the return array:
Note: The array will hold but a single value if the trap was sprung in scalar context, and will be empty if it was in void context.
The captured output on the respective file handles.
Returns undef if the latest trap had no warning-trapping layer; otherwise returns three different views of the warn array:
The context in which the latest code trapped was called. (By default a propagated context, but layers can override this.)
True if the latest code trapped was called in the indicated context. (By default the code will be called in a propagated context, but layers can override this.)
For each accessor, a number of convenient standard test methods are
also available. By default, these are a few standard tests from
Test::More, plus the nok test (a negated ok test). All for
convenience:
INDEX is not optional: It is required for array accessors (like
return and warn), and disallowed for scalar accessors. Note
that the is_deeply test does not accept an index. Even for array
accessors, it operates on the entire array.
For convenience and clarity, tests against a flow control ACCESSOR
(return, die, exit, or any you define yourself) will first
test whether the trap was left by way of the flow control mechanism in
question, and fail with appropriate diagnostics otherwise.
Conveniences: Tests whether the trap was left by way of the flow
control mechanism in question. Much like leaveby_is('die') etc,
but with better diagnostics and (run-time) spell checking.
Convenience: Passes if zero-length output was trapped on both STDOUT and STDERR, and generate better diagnostics otherwise.
Prints a diagnostic message (as per diag in the Test::More manpage) consisting of a dump (in Perl code, as per the Data::Dump manpage) of the trap object.
As diag_all, except if this instance of the trap object has
already been diag_all_once'd, the diagnostic message will instead
consist of the string (as above).
This could be useful with the on_fail layer:
use Test::Trap qw/ :on_fail(diag_all_once) /;
This module must be loaded before any code containing exit()s to be
trapped is compiled. Any exit() already compiled won't be trappable,
and will terminate the program anyway.
This module overrides &CORE::GLOBAL::exit, so may not work correctly
(or even at all) in the presence of other code overriding
&CORE::GLOBAL::exit. More precisely: This module installs its own
exit() on entry of the block, and restores the previous one, if any,
only upon leaving the block.
If you use fork() in the dynamic scope of a trap, beware that the
(default) :exit layer of that trap does not trap exit() in the
children, but passes them to the outer handler. If you think about
it, this is what you are likely to want it to do in most cases.
Note that the (default) :exit layer only traps &CORE::GLOBAL::exit
calls (and bare exit() calls that compile to that). It makes no
attempt to trap CORE::exit(), POSIX::_exit(), exec(), untrapped
exceptions from die(), nor segfault. Nor does it attempt to trap
anything else that might terminate the program. The trap is a block
eval on steroids -- not the last block eval of Krypton!
This module traps warnings using $SIG{__WARN__}, so may not work
correctly (or even at all) in the presence of other code setting this
handler. More precisely: This module installs its own __WARN__
handler on entry of the block, and restores the previous one, if any,
only upon leaving the block.
The (default) :stdout and :stderr handlers will not trap output from
system() calls.
Threads? No idea. It might even work correctly.
Please report any bugs or feature requests directly to the author.
Eirik Berg Hanssen, <ebhanssen@cpan.org>
Copyright 2006-2014 Eirik Berg Hanssen, All Rights Reserved.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
| Test::Trap - Trap exit codes, exceptions, output, etc. |