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Author image Erik Tank


Test::Mock::Simple - A simple way to mock out parts of or a whole module.


  use Test::Mock::Simple;

  my $total = 0;

  # Original::Module has methods increase, decrease, and sum
  my $mock = Test::Mock::Simple->new(module => 'Original::Module');
  $mock->add(increase => sub { shift; return $total += shift; });
  $mock->add(decrease => sub { shift; return $total -= shift; });

  my $obj = Original::Module->new();
  print $obj->sum . "\n"; # prints 3


This is a simple way of overriding any number of methods for a given object/class.

Can be used directly in test (or any) files, but best practice (IMHO) is to create a 'Mock' module and using it instead of directly using the module in any tests. The goal is to write a test which passes whether Mocking is being used or not. See TEST_MOCK_SIMPLE_DISABLE below.

The default behavior is to not allow adding methods that do not exist. This should stop mistyped method names when attempting to mock existing methods. See allow_new_methods below to change this behavior.

Why another Mock module? I needed something simple with no bells or whistles that only overrode certain methods of a given module. It's more work, but there aren't any conflicts.

This module can not do anything about BEGIN, END, or other special name code blocks. To changes these see B's (The Perl Compiler Backend) begin_av, end_av, etc. methods.

Environmental Variables


If set to true (preferably 1) then 'add' is disabled.



Create a new mock simple object.


The name of the module that is being mocked. The module will be loaded immediately (by requiring it).

NOTE: since require is being used to load the module it's import method is not being called. This may change in later versions.


module_location expects a PATHNAME to the file (relative to the @INC paths) which contains the namespace (or module) that you want to mock.

This is useful when a single file declares multiple namespaces or in the event of bad coding where the module's namespace does not map to the module's location.


  use Test::Mock::Simple;

  my $mock = Test::Mock::Simple->new(
    module          => 'Original::Module',
    module_location => 'Modules/Orignal/Module.pm',

To create methods that do not exist in the module that is being mocked.

The default behavior is to not allow adding methods that do not exist. This should stop mistyping method names when attempting to mock existing methods.


Default behavior is to load the real module before overriding individual methods.

If this is not desired set no_load to 1 which will stop this from happening.

If set then you are required to mock the whole module (or at least every command required for code to work).

Setting no_load to 1 will force allow_new_methods to 1 as well. This is done since without the module actually loaded there is no way of knowing what methods the module has.


This allows for the creation of a new method (subroutine) that will override the existing one. Think of it as 'add'ing a mocked method to override the existing one.


Erik Tank, <tank@jundy.com>


Copyright (C) 2020 by Erik Tank

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.14.2 or, at your option, any later version of Perl 5 you may have available.