Quick Navigator

Search Site

Unix VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Contact Us
Online Help
Domain Status
Man Pages

Virtual Servers

Topology Map

Server Agreement
Year 2038

USA Flag



Man Pages

Manual Reference Pages  -  TEST::OUTPUT (3)

.ds Aq ’


Test::Output - Utilities to test STDOUT and STDERR messages.



Version 0.16


    use Test::More tests => 4;
    use Test::Output;

    sub writer {
      print "Write out.\n";
      print STDERR "Error out.\n";

    stdout_is(\&writer,"Write out.\n",Test STDOUT);

    stderr_isnt(\&writer,"No error out.\n",Test STDERR);

                "Write out.\nError out.\n",
                Test STDOUT & STDERR combined

              "Write out.\n",
              "Error out.\n",
              Test STDOUT & STDERR

   # Use bare blocks.

   stdout_is { print "test" } "test", "Test STDOUT";
   stderr_isnt { print "bad test" } "test", "Test STDERR";
   output_is { print STDOUT; print STDERR STDERR }
     "STDOUT", "STDERR", "Test output";


Test::Output provides a simple interface for testing output sent to STDOUT or STDERR. A number of different utilities are included to try and be as flexible as possible to the tester.

Originally this module was designed not to have external requirements, however, the features provided by Sub::Exporter over what Exporter provides is just to great to pass up.

Likewise, Capture::Tiny provides a much more robust capture mechanism without than the original Test::Output::Tie.




   stdout_is  ( $coderef, $expected, description );
   stdout_is    { ... } $expected, description;
   stdout_isnt( $coderef, $expected, description );
   stdout_isnt  { ... } $expected, description;

stdout_is() captures output sent to STDOUT from $coderef and compares it against $expected. The test passes if equal.

stdout_isnt() passes if STDOUT is not equal to $expected.


   stdout_like  ( $coderef, qr/$expected/, description );
   stdout_like    { ... } qr/$expected/, description;
   stdout_unlike( $coderef, qr/$expected/, description );
   stdout_unlike  { ... } qr/$expected/, description;

stdout_like() captures the output sent to STDOUT from $coderef and compares it to the regex in $expected. The test passes if the regex matches.

stdout_unlike() passes if STDOUT does not match the regex.



   stderr_is  ( $coderef, $expected, description );
   stderr_is    {... } $expected, description;

   stderr_isnt( $coderef, $expected, description );
   stderr_isnt  {... } $expected, description;

stderr_is() is similar to stdout_is, except that it captures STDERR. The test passes if STDERR from $coderef equals $expected.

stderr_isnt() passes if STDERR is not equal to $expected.


   stderr_like  ( $coderef, qr/$expected/, description );
   stderr_like   { ...} qr/$expected/, description;
   stderr_unlike( $coderef, qr/$expected/, description );
   stderr_unlike  { ...} qr/$expected/, description;

stderr_like() is similar to stdout_like() except that it compares the regex $expected to STDERR captured from $codref. The test passes if the regex matches.

stderr_unlike() passes if STDERR does not match the regex.



   combined_is   ( $coderef, $expected, description );
   combined_is   {... } $expected, description;
   combined_isnt ( $coderef, $expected, description );
   combined_isnt {... } $expected, description;

combined_is() directs STDERR to STDOUT then captures STDOUT. This is equivalent to UNIXs 2>&1. The test passes if the combined STDOUT and STDERR from $coderef equals $expected.

combined_isnt() passes if combined STDOUT and STDERR are not equal to $expected.


   combined_like   ( $coderef, qr/$expected/, description );
   combined_like   { ...} qr/$expected/, description;
   combined_unlike ( $coderef, qr/$expected/, description );
   combined_unlike { ...} qr/$expected/, description;

combined_like() is similar to combined_is() except that it compares a regex ($expected) to STDOUT and STDERR captured from $codref. The test passes if the regex matches.

combined_unlike() passes if the combined STDOUT and STDERR does not match the regex.



   output_is  ( $coderef, $expected_stdout, $expected_stderr, description );
   output_is    {... } $expected_stdout, $expected_stderr, description;
   output_isnt( $coderef, $expected_stdout, $expected_stderr, description );
   output_isnt  {... } $expected_stdout, $expected_stderr, description;

The output_is() function is a combination of the stdout_is() and stderr_is() functions. For example:

  output_is(sub {print "foo"; print STDERR "bar";},foo,bar);

is functionally equivalent to

  stdout_is(sub {print "foo";},foo)
    && stderr_is(sub {print STDERR "bar";bar);

except that $coderef is only executed once.

Unlike, stdout_is() and stderr_is() which ignore STDERR and STDOUT respectively, output_is() requires both STDOUT and STDERR to match in order to pass. Setting either $expected_stdout or $expected_stderr to undef ignores STDOUT or STDERR respectively.

  output_is(sub {print "foo"; print STDERR "bar";},foo,undef);

is the same as

  stdout_is(sub {print "foo";},foo)

output_isnt() provides the opposite function of output_is(). It is a combination of stdout_isnt() and stderr_isnt().

  output_isnt(sub {print "foo"; print STDERR "bar";},bar,foo);

is functionally equivalent to

  stdout_is(sub {print "foo";},bar)
    && stderr_is(sub {print STDERR "bar";foo);

As with output_is(), setting either $expected_stdout or $expected_stderr to undef ignores the output to that facility.

  output_isnt(sub {print "foo"; print STDERR "bar";},undef,foo);

is the same as

  stderr_is(sub {print STDERR "bar";},foo)


  output_like  ( $coderef, $regex_stdout, $regex_stderr, description );
  output_like  { ... } $regex_stdout, $regex_stderr, description;
  output_unlike( $coderef, $regex_stdout, $regex_stderr, description );
  output_unlike { ... } $regex_stdout, $regex_stderr, description;

output_like() and output_unlike() follow the same principles as output_is() and output_isnt() except they use a regular expression for matching.

output_like() attempts to match $regex_stdout and $regex_stderr against STDOUT and STDERR produced by $coderef. The test passes if both match.

  output_like(sub {print "foo"; print STDERR "bar";},qr/foo/,qr/bar/);

The above test is successful.

Like output_is(), setting either $regex_stdout or $regex_stderr to undef ignores the output to that facility.

  output_like(sub {print "foo"; print STDERR "bar";},qr/foo/,undef);

is the same as

  stdout_like(sub {print "foo"; print STDERR "bar";},qr/foo/);

output_unlike() test pass if output from $coderef doesn’t match $regex_stdout and $regex_stderr.


By default, all tests are exported, however with the switch to Sub::Exporter export groups are now available to better limit imports.

To import tests for STDOUT:

  use Test::Output qw(:stdout);

To import tests STDERR:

  use Test::Output qw(:stderr);

To import just the functions:

  use Test::Output qw(:functions);

And to import all tests:

  use Test::Output;

The following is a list of group names and which functions are exported:
stdout stdout_is stdout_isnt stdout_like stdout_unlike
stderr stderr_is stderr_isnt stderr_like stderr_unlike
output output_is output_isnt output_like output_unlike
combined combined_is combined_isnt combined_like combined_unlike
tests All of the above, this is the default when no options are given.
Sub::Exporter allows for many other options, I encourage reading its documentation.



  my $stdout = stdout_from($coderef)
  my $stdout = stdout_from { ... };

stdout_from() executes $coderef and captures STDOUT.


  my $stderr = stderr_from($coderef)
  my $stderr = stderr_from { ... };

stderr_from() executes $coderef and captures STDERR.


  my ($stdout, $stderr) = output_from($coderef)
  my ($stdout, $stderr) = output_from {...};

output_from() executes $coderef one time capturing both STDOUT and STDERR.


  my $combined = combined_from($coderef);
  my $combined = combined_from {...};

combined_from() executes $coderef one time combines STDOUT and STDERR, and captures them. combined_from() is equivalent to using 2>&1 in UNIX.


Currently maintained by brian d foy,

Shawn Sorichetti, <>


This module is in Github:


Please report any bugs or feature requests to, or through the web interface at <>. I will be notified, and then you’ll automatically be notified of progress on your bug as I make changes.


Thanks to chromatic whose was the basis for capturing output.

Also thanks to rjbs for his help cleaning the documentation, and pushing me to Sub::Exporter.

Thanks to David Wheeler for providing code block support and tests.

Thanks to Michael G Schwern for the solution to combining STDOUT and STDERR.


Copyright 2005-2013 Shawn Sorichetti, All Rights Reserved.

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

Search for    or go to Top of page |  Section 3 |  Main Index

perl v5.20.3 TEST::OUTPUT (3) 2014-01-03

Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.