Test::MockModule(3) Override subroutines in a module for unit testing


use Module::Name;
use Test::MockModule;
my $module = Test::MockModule->new('Module::Name');
$module->mock('subroutine', sub { ... });
Module::Name::subroutine(@args); # mocked
Module::Name::subroutine(@args); # original subroutine
# Working with objects
use Foo;
use Test::MockModule;
my $mock = Test::MockModule('Foo');
$mock->mock(foo => sub { print "Foo!\n"; });
my $foo = Foo->new();
$foo->foo(); # prints "Foo!\n"


"Test::MockModule" lets you temporarily redefine subroutines in other packages for the purposes of unit testing.

A "Test::MockModule" object is set up to mock subroutines for a given module. The object remembers the original subroutine so it can be easily restored. This happens automatically when all MockModule objects for the given module go out of scope, or when you "unmock()" the subroutine.


new($package[, %options])
Returns an object that will mock subroutines in the specified $package.

If there is no $VERSION defined in $package, the module will be automatically loaded. You can override this behaviour by setting the "no_auto" option:

        my $mock = Test::MockModule->new('Module::Name', no_auto => 1);
Returns the target package name for the mocked subroutines
Returns a boolean value indicating whether or not the subroutine is currently mocked
mock($subroutine => \&coderef)
Temporarily replaces one or more subroutines in the mocked module. A subroutine can be mocked with a code reference or a scalar. A scalar will be recast as a subroutine that returns the scalar.

The following statements are equivalent:

        $module->mock(purge => 'purged');
        $module->mock(purge => sub { return 'purged'});

When dealing with references, things behave slightly differently. The following statements are NOT equivalent:

        # Returns the same arrayref each time, with the localtime() at time of mocking
        $module->mock(updated => [localtime()]);
        # Returns a new arrayref each time, with up-to-date localtime() value
        $module->mock(updated => sub { return [localtime()]});

The following statements are in fact equivalent:

        my $array_ref = [localtime()]
        $module->mock(updated => $array_ref)
        $module->mock(updated => sub { return $array_ref });

However, "undef" is a special case. If you mock a subroutine with "undef" it will install an empty subroutine

        $module->mock(purge => undef);
        $module->mock(purge => sub { });

rather than a subroutine that returns "undef":

        $module->mock(purge => sub { undef });

You can call "mock()" for the same subroutine many times, but when you call "unmock()", the original subroutine is restored (not the last mocked instance).


If you are trying to mock a subroutine exported from another module, this may not behave as you initialy would expect, since Test::MockModule is only mocking at the target module, not anything importing that module. If you mock the local package, or use a fully qualified function name, you will get the behavior you desire:

        use Test::MockModule;
        use Test::More;
        use POSIX qw/strftime/;
        my $posix = Test::MockModule->new("POSIX");
        $posix->mock("strftime", "Yesterday");
        is strftime("%D", localtime(time)), "Yesterday", "`strftime` was mocked successfully"; # Fails
        is POSIX::strftime("%D", localtime(time)), "Yesterday", "`strftime` was mocked successfully"; # Succeeds
        my $main = Test::MockModule->new("main", no_auto => 1);
        $main->mock("strftime", "today");
        is strftime("%D", localtime(time)), "today", "`strftime` was mocked successfully"; # Succeeds

If you are trying to mock a subroutine that was exported into a module that you're trying to test, rather than mocking the subroutine in its originating module, you can instead mock it in the module you are testing:

        package MyModule;
        use POSIX qw/strftime/;
        sub minus_twentyfour
                return strftime("%a, %b %d, %Y", localtime(time - 86400));
        package main;
        use Test::More;
        use Test::MockModule;
        my $posix = Test::MockModule->new("POSIX");
        $posix->mock("strftime", "Yesterday");
        is MyModule::minus_twentyfour(), "Yesterday", "`minus-tewntyfour` got mocked"; # fails
        my $mymodule = Test::MockModule->new("MyModule", no_auto => 1);
        $mymodule->mock("strftime", "Yesterday");
        is MyModule::minus_twentyfour(), "Yesterday", "`minus-tewntyfour` got mocked"; # suceeds
Returns the original (unmocked) subroutine
unmock($subroutine [, ...])
Restores the original $subroutine. You can specify a list of subroutines to "unmock()" in one go.
Restores all the subroutines in the package that were mocked. This is automatically called when all "Test::MockObject" objects for the given package go out of scope.


Current Maintainer: Geoff Franks <[email protected]>

Original Author: Simon Flack <simonflk _AT_ cpan.org>


Copyright 2004 Simon Flack <simonflk _AT_ cpan.org>. All rights reserved

You may distribute under the terms of either the GNU General Public License or the Artistic License, as specified in the Perl README file.