Test::Mock::Class - Simulating other classes


  use Test::Mock::Class ':all';
  require Net::FTP;

  # concrete mocked class
  mock_class 'Net::FTP' => 'Net::FTP::Mock';
  my $mock_object = Net::FTP::Mock->new;

  # anonymous mocked class
  my $metamock = mock_anon_class 'Net::FTP';
  my $mock_object = $metamock->new_object;

  # anonymous class with role applied
  my $metamock = Test::Mock::Class->create_anon_class(
      roles => [ 'My::Handler::Role' ],
  my $mock_object = $metamock->new_object;


In a unit test, mock objects can simulate the behavior of complex, real (non-mock) objects and are therefore useful when a real object is impractical or impossible to incorporate into a unit test.

The unique features of Test::Mock::Class:

  • Its API is inspired by PHP SimpleTest framework.

  • It isn't tied with Test::Builder so it can be used standalone or with any xUnit-like framework, i.e. Test::Unit::Lite. Look for Test::Builder::Mock::Class if you want to use it with Test::Builder (Test::More or Test::Simple).

  • The API for creating mock classes is based on Moose and Class::MOP so it doesn't clash with API of original class and is easy expandable.

  • The methods for defining mock object's behavior are prefixed with mock_ string so they shouldn't clash with original object's methods.

  • Mocks as actors: The mock version of a class has all the methods of the original class. The return value will be undef, but it can be changed with mock_returns method.

  • Mocks as critics: The method of mock version of a class can check its calling arguments and throws an exception if arguments don't match (mock_expect method). An exception also can be thrown if the method wasn't called at all (mock_expect_once method).



mock_class( class : Str, mock_class : Str = undef ) : Moose::Meta::Class

Creates the concrete mock class based on original class. If the name of mock_class is undefined, its name is created based on name of original class with added ::Mock suffix.

The original class is loaded with Class::MOP::load_class function which behaves wrongly for some packages, i.e. IO::File. It is much safer to require original class explicitly.

The function returns the metaclass object of new mock_class.

mock_anon_class( class : Str = undef ) : Moose::Meta::Class

Creates an anonymous mock class based on original class. The name of this class is automatically generated. If class argument not defined, the empty mock class is created.

The function returns the metaobject of new mock class.


Test::Mock::Class ':all';

Imports all functions into caller's namespace.


The Test::Mock::Class fits perfectly to Test::Unit::Lite tests. It throws an exception immediately if some problem is occurred. It means that the test unit is failed if i.e. the mock method is called with wrong arguments.

Example code:

  package My::ExampleTest;

  use Test::Unit::Lite;

  use Moose;
  extends 'Test::Unit::TestCase';

  use Test::Assert ':all';
  use Test::Mock::Class ':all';

  require IO::File;

  sub test_mock_class {
      my ($self) = @_;

      my $mock = mock_anon_class 'IO::File';
      my $io = $mock->new_object;
      $io->mock_return( open => 1, args => [qr//, 'r'] );

      assert_true( $io->open('/etc/passwd', 'r') );



Mock metaclass API: Test::Mock::Class::Role::Meta::Class, Moose::Meta::Class.

Mock object methods: Test::Mock::Class::Role::Object.

xUnit-like testing: Test::Unit::Lite.

Mock classes for Test::Builder: Test::Builder::Mock::Class.

Other implementations: Test::MockObject, Test::MockClass.


The API is not stable yet and can be changed in future.


Piotr Roszatycki <>


Based on SimpleTest, an open source unit test framework for the PHP programming language, created by Marcus Baker, Jason Sweat, Travis Swicegood, Perrick Penet and Edward Z. Yang.

Copyright (c) 2009, 2010 Piotr Roszatycki <>.

This program is free software; you can redistribute it and/or modify it under GNU Lesser General Public License.