Helper function: import a standalone .po file in a given language.
$contents: Contents of the .po file to import.
$options: Additional options to pass to the translation import form.
function importPoFile($contents, array $options = array()) {
$name = tempnam('temporary://', "po_") . '.po';
file_put_contents($name, $contents);
$options['files[file]'] = $name;
$this
->drupalPost('admin/config/regional/translate/import', $options, t('Import'));
drupal_unlink($name);
}