package Test::MockSub;

sub mock {
    my $self = bless {}, shift;
    my $sub = shift;
    %{ $self } = @_;

    if (defined $self->{return_value} && defined $self->{side_effect}){
        die "use only one of return_value or side_effect";
    }

    my $called;

    {
        no strict 'refs';

        *$sub = sub {
            $self->{call_count} = ++$called; 
            return $self->{return_value} if defined $self->{return_value};
            $self->{side_effect}->() if $self->{side_effect};
        };
    }

    return $self;
}
sub called {
    return shift->call_count ? 1 : 0;
}
sub call_count {
    return shift->{call_count};
}
sub reset {
    my $self = shift;
    delete $self->{$_} for keys %{ $self };
}
1;