package Krautcat;
use strict; use warnings;
use Moo;
use MooX::TypeTiny;:
use Types::Standard qw/ Str is_Str /;

has foo => ( is => 'ro', isa => Str, required => 1 );
has baz => ( is => 'rw', );

sub qux {
    my $self = shift;
    my $val = shift;

    die 'not a string' if not is_Str $val;
    $self->baz( $val );

    return { baz => $self->baz };
}

1;

##</code><code>##

use strict; use warnings;
use Test::Most;

use_ok 'Krautcat', 'Loaded class';

throws_ok(
    sub { my $obj = Krautcat->new() },
    qr/Missing required arguments: foo/,
    'empty params throws ok',
);

dies_ok(
    sub { my $obj = Krautcat->new( foo => [42] ) },
    'non-string param for constructor dies ok',
);

like(
    $@,
    qr/\QReference [42] did not pass type constraint "Str"\E/,
    'assertion failure message looks ok',
);

my $obj = new_ok(
    'Krautcat' => [ foo => 'bar' ],
    'obj with valid constructor params',
);

is( $obj->foo, 'bar', 'attr has correct val from constructor' );

throws_ok(
    sub { $obj->qux( [42] ) },
    qr/not a string/,
    'non-string param for qux() throws ok',
);

lives_and(
    sub { is_deeply $obj->qux('blorg'), { baz => 'blorg' } },
    'string param for qux() validates ok',
);

done_testing;


##</code><code>##

prove -v 1199413.pl
1199413.pl .. 
ok 1 - use Krautcat;
ok 2 - empty params throws ok
ok 3 - non-string param for constructor dies ok
ok 4 - assertion failure message looks ok
ok 5 - 'obj with valid constructor params' isa 'Krautcat'
ok 6 - attr has correct val from constructor
ok 7 - non-string param for qux() throws ok
ok 8 - string param for qux() validates ok
1..8
ok
All tests successful.
Files=1, Tests=8,  0 wallclock secs ( 0.01 usr  0.01 sys +  0.08 cusr  0.01 csys =  0.11 CPU)
Result: PASS