Multiple errors on Debian 8

[Fr33maan]

My initial config:

class { 'rkhunter':
    mail_on_warning => 'root',
}

First I got this error:

Error: Failed to parse template rkhunter/etc/rkhunter.conf.erb:
  Filepath: /etc/puppet/modules/rkhunter/templates/etc/rkhunter.conf.erb
  Line: 42
  Detail: undefined method `each' for "all":String
 at /etc/puppet/modules/rkhunter/manifests/config.pp:12 on node test-mailname

So I've put in my manifest:

class { 'rkhunter':
    mail_on_warning => 'root',
    enable_tests    => ['all']
}

Then I'm getting this error:

Error: Failed to parse template rkhunter/etc/rkhunter.conf.erb:
  Filepath: /etc/puppet/modules/rkhunter/templates/etc/rkhunter.conf.erb
  Line: 74
  Detail: undefined method `each' for "root":String
 at /etc/puppet/modules/rkhunter/manifests/config.pp:12 on node test-mailname

So I've done:

class { 'rkhunter':
    mail_on_warning => ['root'],
    enable_tests    => ['all']
}

But now I'm getting another error, something related with mail command:

Notice: /Stage[main]/Rkhunter::Exec/Exec[RKHunter_Scan]/returns: Invalid MAIL_CMD configuration option: command is non-existent or not executable: mail
Error: /Stage[main]/Rkhunter::Exec/Exec[RKHunter_Scan]: Failed to call refresh: rkhunter --cronjob --report-warnings-only returned 1 instead of one of [0]
Error: /Stage[main]/Rkhunter::Exec/Exec[RKHunter_Scan]: rkhunter --cronjob --report-warnings-only returned 1 instead of one of [0]

1. It would be better if I didn't need to include enable_tests in my manifest.
2. Yes, mail is not available but sendmail is. Should I also install mailutils for this module to work ? If so it should be a dependency right ?

Thanks for your job !