🌻 📖 Test2::Tools::Process


Test2::Tools::Process - Unit tests for code that calls exit, exec, system or qx()


version 0.07


 use Test2::V0 -no_srand => 1;
 use Test2::Tools::Process;
 process {
   system 'foo', 'bar';
 } [
   # check that the first system call is to
   # a command foo with any arguments
   proc_event(system => array {
     item 'foo';
   }, sub {
     # simulate the foo command
     my($proc, @args) = @_;
     note "faux bar command: @args";
     # simulate a normal exit
 process {
   exit 2;
   note 'not executed';
 } [
   # can use any Test2 checks on the exit status
   proc_event(exit => match qr/^[2-3]$/),
 process {
   exit 4;
 } [
   # or you can just check that the exit status matches numerically
   proc_event(exit => 4),
 process {
   exit 5;
 } [
   # or just check that we called exit.
 process {
   exec 'foo bar';
   exec 'baz';
   note 'not executed';
 } [
   # emulate first exec as failed
   proc_event(exec => match qr/^foo\b/, sub {
     my($return, @command) = @_;
     $! = 2;
     return 0;
   # the second exec will be emulated as successful
 # just intercept `exit`
 is intercept_exit { exit 10 }, 10;
 # just intercept `exec`
 is intercept_exec { exec 'foo', 'bar', 'baz' }, ['foo','bar','baz'];


This set of testing tools is intended for writing unit tests for code that interacts with other processes without using real processes that might have unwanted side effects. It also lets you test code that exits program flow without actually terminating your test. So far it allows you to test and/or mock exit, exec, system, readpipe and qx//. Other process related tests will be added in the future.

This module borrows some ideas from Test::Exit. In particular it does not use exceptions to simulate exit or exec, so you can freely test code that calls these in an eval.



 my $ok = process { ... } \@events, $test_name;
 my $ok = process { ... } \@events;
 my $ok = process { ... } $test_name;
 my $ok = process { ... };

Runs the block, intercepting exit, exec, system, readpipe and qx// calls. The calls are then matched against \@events as the expected process events. See proc_event below for defining individual events, and the synopsis above for examples.


 my $signame = named_signal $name;

Given a string signal name like KILL, this will return the integer signal number. It will throw an exception if the $name is invalid.


 my $status = intercept_exit { ... };

Intercept any c<exit> calls inside the block, and return the exit status. Returns undef if there were no exec calls.


 my $arrayref = intercept_exec { ... };

Intercept any exec calls inside the block and return the command line that a was passed to it. Returns undef if there were no exec calls.



 process { ... } [
   proc_event($type => $check, $callback),
   proc_event($type => $check),
   proc_event($type => $callback),
   # additional result checks for `system` events
   proc_event('system' => $check, \%result_check, $callback),
   proc_event('system' => \%result_check, $callback),
   proc_event('system' => $check, \%result_check),
   proc_event('system' => \%result_check),

The proc_event function creates a process event, with an optional check and callback. How the $check works depends on the $type. If no $check is provided then it will only check that the $type matches. Due to their nature, exit and exec events are emulated. system events will actually make a system call, unless a $callback is provided.


A process event for an exit call. The check is against the status value passed to exit. This value will always be an integer. If no status value was passed to exit, 0 will be used as the status value.

If no callback is provided then an exit will be emulated by terminating the process block without executing any more code. The rest of the test will then proceed.

 proc_event( exit => sub {
   my($proc, $status) = @_;

The callback takes a $proc object and a $status value. Normally exit should never return, so what you want to do is call the terminate method on the $proc object.


A process event for an exec call. The check is against the command passed to exec. If exec is called with a single argument this will be a string, otherwise it will be an array reference. This way you can differentiate between the SCALAR and LIST modes of exec.

If no callback is provided then a (successful) exec will be emulated by terminating the process block without executing any more code. The rest of the test will then proceed.

 proc_event( exec => sub {
   my($proc, @command) = @_;

The callback takes a $proc object and the arguments passed to exec as @command. You can emulate a failed exec by using the errno method on the $proc object:

 proc_event( exec => sub {
   my($proc, @command) = @_;
   $proc->errno(2); # this is the errno value

To emulate a successful exec call you want to just remember to call the terminate method on the $proc object.

 proc_event( exec => sub {
   my($proc, @command) = @_;

A process event for system, piperead and qx//. The first check (as with exec) is against the command string passed to system. The second is a hash reference with result checks.

 proc_event( system => { status => $check } );

The normal termination status. This is usually the value passed to exit in the program called. Typically a program that succeeded will return zero (0) and a failed on will return non-zero.

 proc_event( system => { errno => $check } );

The errno or $! value if the system call failed. Most commonly this is for bad command names, but it could be something else like running out of memory or other system resources.

 proc_event( system => { signal => $check } );

Set if the process was killed by a signal.

Only one check should be included because only one of these is usually valid. If you do not provide this check, then it will check that the status code is zero only.

By default the actual system call will be made, but if you provide a callback you can simulate commands, which is helpful in unit testing your script without having to call external programs which may have unwanted side effects.

 proc_event( system => sub {
   my($proc, @command) = @_;

Like the exec event, @command contains the full command passed to the system call. You can use the $proc object to simulate one of three different results:


Exit with the given status. A status of zero (0) will be used if not provided. If no result is specified in the callback at all then a status of zero (0) will also be used.


Terminate with the given signal. $signal can be either an integer value (in which case no validation that it is a real signal is done), or a string signal name like KILL, HUP or any signal supported by your operating system. If you provide an invalid signal name an exception will be thrown.

 proc_event( system => { signal => 9 } => sub {
   my($proc, @args) = @_;

Note that when you kill one of these faux processes with a signal you will want to update the expected signal check, as in the example above.


Simulate a failed system call. Most often system will fail if the command is not found. The $errno passed in should be a valid errno value. On my system 2 is the error code for command not found. Example:

 proc_event( system => { errno => number(2) } => sub {
   my($proc, @args) = @_;
 my $type = $proc->type;

Returns system or readpipe depending on the Perl function that triggered the system call.


The exit emulation, doesn't call END callbacks or other destructors, since you aren't really terminating the process.

This module installs handlers for exec, exit, system and readpipe, in the CORE::GLOBAL namespace, so if your code is also installing handlers there then things might not work.

This module is not apparently compatible with IPC::Run3. Use Capture::Tiny instead, which is better maintained in my opinion.



Simple exit emulation for tests. The most recent version does not rely on exceptions.


Like Test::Exit, but for exec


Provides an interface to mocking system, qx and exec.


Author: Graham Ollis <plicease@cpan.org>


Jeremy Mates (THRIG)


This software is copyright (c) 2015-2022 by Graham Ollis.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.