The Perl Toolchain Summit needs more sponsors. If your company depends on Perl, please support this very important event.
use Moo::_strictures;
use Test::More;

{
  package MyClassRoot;
  use Moo;
  has root => (is => 'ro');
}

{
  package MyClassLeft;
  use Moo;
  extends 'MyClassRoot';
  has left => (is => 'ro');
}

{
  package MyClassRight;
  use Moo;
  extends 'MyClassRoot';
  has right => (is => 'ro');
}

{
  package MyClassChild;
  use Moo;
  extends 'MyClassLeft', 'MyClassRight';
  has child => (is => 'ro');
}

my $o = MyClassChild->new(root => 1, left => 2, right => 3, child => 4);
is $o->root, 1, 'constructor populates root class attribute';
is $o->left, 2, 'constructor populates left parent attribute';
is $o->right, undef, 'constructor doesn\'t populate right parent attribute';
is $o->child, 4, 'constructor populates child class attribute';

done_testing;