Add t/lib/Mo and a bunch of tests

t/lib/Mo/build.t

@@ -0,0 +1,51 @@
+#!/usr/bin/perl
+
+BEGIN {
+   die "The PERCONA_TOOLKIT_BRANCH environment variable is not set.\n"
+      unless $ENV{PERCONA_TOOLKIT_BRANCH} && -d $ENV{PERCONA_TOOLKIT_BRANCH};
+   unshift @INC, "$ENV{PERCONA_TOOLKIT_BRANCH}/lib";
+};
+
+use strict;
+use warnings FATAL => 'all';
+use English qw(-no_match_vars);
+use Test::More;
+
+$main::count = 1;
+
+package Foo;
+use Mo 'build';
+has 'foo' => (is => 'rw');
+sub BUILD {
+    my $self = shift;
+    ::is_deeply(\@_, [qw(stuff 1)], "Foo's BUILD doesn't get the class name");
+    $self->foo($main::count++);
+}
+
+package Bar;
+use Mo;
+extends 'Foo';
+has 'bar' => (is => 'rw');
+
+package Baz;
+use Mo;
+extends 'Bar';
+has 'baz' => (is => 'rw');
+sub BUILD {
+    my $self = shift;
+    ::is_deeply(\@_, [qw(stuff 1)], "Baz's BUILD doesn't get the class name");
+    $self->baz($main::count++);
+}
+
+package Gorch;
+use Mo;
+extends 'Baz';
+has 'gorch' => (is => 'rw');
+
+package main;
+
+my $g = Gorch->new(stuff => 1);
+is $g->foo, 1, 'foo builds first';
+is $g->baz, 2, 'baz builds second';
+
+done_testing;