Test::Subs - Test your modules with a lightweight anonymous block based syntax


  use SomeModule;
  use Test::Subs;
  test { 1 == 2 };


This module provide a very lightweight syntax to run Test::Harness or Tap::Harness compliant test on your code.

As opposed to other similar packages, the two main functionnalities of Test::Subs are that the tests are anonymous code block (rather than list of values), which are (subjectively) cleaner and easier to read, and that you do not need to pre-declare the number of tests that are going to be run (so all modifications in a test file are local).

Using this module is just a matter of use Test::Subs followed by the declaration of your tests with the functions described below. All tests are then run at the end of the execution of your test file.

As a protection against some error, if the compilation phase fail, the output of the test file will be one failed pseudo-test.


This is a list of the public function of this library. Functions not listed here are for internal use only by this module and should not be used in any external code unless .

All the functions described below are automatically exported into your package except if you explicitely request to opposite with use Test::Subs ();.

Finally, these function must all be called from the top-level and not inside of the code of another test function. That is because the library must know the number of test before their execution.


  test { CODE };
  test { CODE } DESCR;

This function register a code-block containing a test. During the execution of the test, the code will be run and the test will be deemed successful if the returned value is true.

The optionnal DESCR is a string (or an expression returning a string) which will be added as a comment to the result of this test. If this string contains a printf conversion (e.g. %s or %d) it will be replaced by the result of the code block. If the description is omitted, it will be replaced by the filename and line number of the test. You can use an empty string '' to deactivate completely the output of a comment to the test.


  todo { CODE };
  todo { CODE } DESCR;

This function is the same as the function test, except that the test will be registered as to-do. So a failure of this test will be ignored when your test is run inside a test plan by Test::Harness or Tap::Harness.


  match { CODE } REGEXP;
  match { CODE } REGEXP, DESCR;

This function declares a test which will succeed if the result of the code block match the given regular expression.

The regexp may be given as a scalar string or as a qr encoded regexp.


  not_ok { CODE };
  not_ok { CODE } DESCR;

This function is exactly the opposite of the test one. The test that it declares will succeed if the code block return a false value.


  fail { CODE };
  fail { CODE } DESCR;

This function declares a test that will succeed if its code block die (raise any exception).


  failwith { CODE } REGEXP;
  failwith { CODE } REGEXP, DESCR;

As for the fail function, this function declares a test which expects that its code block die. Except that the test will succeed only if the raised exception (the content of the $@ variable) match the given regular expression.

The regexp may be given as a scalar string or as a qr encoded regexp.


  comment { CODE };

This function evaluate its code and display the resulting value on the standard error handle. The buffering on STDOUT and STDERR is deactivated when Test::Subs is used and the output of this function should appear in between the result of the test when the test file is run stand-alone.

This function must be used outside of the code the other functions described above. The output comment to STDERR inside a test, just use the print or printf function. The default output has been select-ed to STDERR so the result of the test will not be altered.


  debug { CODE } DESCR;

This function register and executes a dummy test: the CODE is executed and error messages (if any) are written on STDERR but the test always succeed.

Usefull when a test fail to quickly see what is going on.


Here is an example of a small test file using this module.

  use strict;
  use warnings;
  use Test::Subs;
  test { 1 == 1 } 'This is the first test';
  todo { 1 == 2 };
  not_ok { 0 };
  fail { die "fail" };

Run through Test::Harness this file will pass, with only the second test failing (but marked todo so that's OK).


This package does not use the Test::Builder facility and as such is not compatible with other testing modules are using Test::Builder. This may be changed in a future release.

The standard set by Test::Harness is that all output to STDOUT is interpreted by the test parser. So a test file should write additional output only to STDERR. This is what will be done by the comment fonction. To help with this, during the execution of your test file, the STDERR file-handle will be select-ed. So any un-qualified print or printf call will end in STDERR.

This package use source filtering (with Filter::Simple). The filter applied is very simple, but there is a slight possibility that it is incompatible with other source filter. If so, do not hesitate to report this as a bug.


Please report any bugs or feature requests to, or through the web interface at


Test, Test::Tiny, Test::Lite, Test::Simple


Mathias Kende (


Version 0.02 (January 2013)


Copyright 2013 © Mathias Kende. All rights reserved.

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