I'm working on a protocol implementation for which the previous maintainer wrote no unit tests whatsoever. To get any reasonable amount of coverage, I need to mock IO::Socket::INET. The actual mocked routines will be easy: mainly just scripted send()/recv() sequences with a few refused connections, timeouts and disconnects thrown in for good measure. The unexpectedly hard part seems to be actually mocking IO::Socket::INET in a useful way.

Since IO::Socket::INET->new() actually initiates a connection, and the connection handshaking for my protocol is important to test (so I can't just skip it and shove in my own object in place of a connected socket), I need to mock new() as well. So, I went for Test::MockModule, but the methods I've mocked appear to be nonexistent ("Can't locate object method..."). Not even calling the original method.

I've boiled down my efforts into a single source file (below). The idea is that I'm able to call mock_me() (normally from an included lib/helper.pl file) with custom subs for IO::Socket::INET, but it returns an instance of My::Module. The real code has more logic to do custom/conditional send()/recv() chains and the like, but the code below illustrates the idea, and more importantly, the problem. Anything much more complex than the examples given in Test::MockModule's synopsis seems to fail, even in the same scope, or passing scalar refs around.

How do I make a sensible mocked up framework for IO::Socket::INET? As it stands now, I'm leaning towards forgetting about Test::MockModule and just doing my own thing, but I'd rather believe this is a solved problem and I'm just doing it wrong.

Not that it matters for this example, but my real code uses IO::Socket::INET entirely with the OO interface. No <$socket> mumbo-jumbo.

#!perl -T
use 5.010;
use strict;
use warnings;

## My::Module - Module I'm writing unit tests for

package My::Module;

use Carp;
use IO::Socket 1.18;

sub new { my $class = shift; bless { }, $class }

sub connect {
    my $s = shift;
    $s->{socket} = IO::Socket::INET->new(
        PeerAddr => '127.0.0.1',
        PeerPort => 8080,
        Proto    => 'tcp',
    ) or croak "Connection failed: $!";

    croak 'Invalid handshake' unless $s->{socket}->recv eq 'Hiya!';
    $s->{socket}->send('Howdy!');
    croak 'ACK barf' unless $s->{socket}->recv eq 'Welcome';

    1;
}


## main - Reasonable facsimile for t/02-connect.t

package main;

use Test::More;
use Test::MockModule;

my $obj = mock_me(
    send => sub { $_[0]->{howdy} = 1 if $_[1] eq 'Howdy!' },
    recv => sub { $_[0]->{howdy} ? 'Welcome' : 'Hiya!'    },
);

is 'My::Module', ref $obj, 'Correct module';
lives_ok { $obj->connect } 'Connection and handshake success';

done_testing;

# Mock for IO::Socket::INET with the provided overrides
sub mock_me {
    my $mock = Test::MockModule->new('IO::Socket::INET');

    my %mock = (
        new  => sub { $mock },
        send => sub { warn "send($_[0])" },
        recv => sub { warn "recv" },
        @_
    );

    $mock->mock($_ => $mock{$_}) for keys %mock;

    My::Module->new;
}

__END__
ok 1 - Correct module
Can't locate object method "recv" via package "Test::MockModule" at te
+st.pl line 24.
# Tests were run but no plan was declared and done_testing() was not s
+een.
# Looks like your test exited with 255 just after 1.
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