TDD use Perl ref: http://qiita.com/ishiduca/items/c587307ef61c5cf9ae19

basic.t

use strict;
use utf8;

BEGIN {
    binmode STDOUT, ":utf8";
    binmode STDERR, ":utf8";
}

use Greeter;
use Test::More;
use Test::MockDateTime;

subtest 'Greeter->new で インスタンスの生成ができているか' => sub {
    my $g = Greeter->new;

    ok $g, 'my $g = Greeter->new';
    ok $g->greet, '$g has "greet" method';
};

subtest '$g->greet で時刻に合わせた適切な挨拶を返すか' => sub {
    my $g   = Greeter->new;
    my $ymd = '2013-01-01';

    my $_050000 = "$ymd 05:00:00";
    on $_050000 => sub {
        is $g->greet, 'Good Morning', "$_050000 => Good Morning";
    };

    my $_115959 = "$ymd 11:59:59";
    on $_115959 => sub {
        is $g->greet, 'Good Morning', "$_115959 => Good Morning";
    };

    my $_120000 = "$ymd 12:00:00";
    on $_120000 => sub {
        is $g->greet, 'Good Afternoon', "$_120000 => Good Afternoon";
    };

    my $_180000 = "$ymd 18:00:00";
    on $_180000 => sub {
        is $g->greet, 'Good Evening', "$_180000 => Good Evening";
    };

    my $_045959 = "$ymd 04:59:59";
    on $_045959 => sub {
        is $g->greet, 'Good Evening', "$_045959 => Good Evening";
    };
};

done_testing;

cpanfile

requires 'perl', '5.008001';

requires 'DateTime', '1.06';

on 'test' => sub {
    requires 'Test::More', '0.98';
    requires 'Test::MockDateTime', '0.02';
};

Dest.pm

package Greeter;
use 5.008005;
use strict;
use Carp;

our $VERSION = "0.01";

sub new {
    my $class = shift;
    bless +{} => $class;
};

1;

file0.txt

$ minil new Dest # Dest はディストリビューション名。適当な名前をつける
$ cd Dest

file1.txt

$ vi cpanfile

file11.txt

# cartonで依存モジュールを管理している場合
$ carton exec -- prove -lv

# cpanm (か cpan, cpanplusでモジュール)をインストールしている場合
$ prove -lv

file12.txt

t/00_compile.t .. 
ok 1 - use Greeter;
1..1
ok
t/basic.t ....... 
    # Subtest: newメソッドでインスタンスを作れるか
    ok 1 - $dest = Dest->new
    1..1
ok 1 -  Subtest: newメソッドでインスタンスを作れるか
1..1
ok
All tests successful.
Files=2, Tests=2,  0 wallclock secs ( 0.03 usr  0.01 sys +  0.31 cusr  0.03 csys =  0.38 CPU)
Result: PASS

file13.txt

$ pfswatch . -e carton -- prove -lv

file14.txt

$ pfswatch . -e carton -- prove -PPretty -lv

file3.txt

$ cpanm --installdeps

file4.txt

$ carton install

file5.txt

$ vi t/basic.t

file7.txt

$ carton exec -- prove -lv

file8.txt

$ carton exec -- prove -PPretty -lv # カラフルで見やすい

file9.txt

$ vi lib/Dest.pm

Gretter.pm

package Greeter;
use 5.008005;
use strict;
use Carp;

use DateTime;

our $VERSION = "0.01";

sub new {
    my $class = shift;

    bless {
        time_zone => 'Asia/Tokyo',
        greets => [ 'Good Morning', 'Good Afternoon', 'Good Evening' ],
    }, $class;
};

sub greet {
    my $self = shift;
    my $now  = DateTime->now( time_zone => $self->{time_zone} );
    $self->{greets}[ $self->_get_index($now) ];
};

sub _get_index {
    my $self = shift;
    my $now  = shift;
    my $offset = ($now->hour * 60 + $now->minute);

    ($offset >= (60 * 18)) ? 2 :
    ($offset >= (60 * 12)) ? 1 :
    ($offset >= (60 *  5)) ? 0 : 2;
};

1;