manifests_init.pp

class jdktest (
  $versions = $jdktest::params::versions,
) inherits jdktest::params {
  $package_names = prefix($versions, 'openjdk')

  validate_array($versions)
  validate_array($package_names)

  contain jdktest::install
}

manifests_install.pp

class jdktest::install inherits jdktest {
  if ! ($versions) {
    fail("You didn't provide any jdk versions to be installed")
  }
  validate_array($versions)
  validate_array($package_names)

  package { $package_names:
    ensure  => present,
  }
}

manifests_params.pp

class jdktest::params {
  $versions = [ '7' ]
}

tests_default-test.pp

include jdktest

tests_error-test.pp

class { 'jdktest':
  versions => '7',
}

tests_explicit-default-test.pp

class { 'jdktest':
  versions => [ '7' ],
}

tests_two-package-test.pp

class { "jdktest":
  versions => [ '7', '8' ],
}