Tests upgrading translations without plurals.
public function testLanguageNoPluralsUpgrade() {
// Remove all plural translations from the database.
db_delete('locales_target')
->condition('plural', 0, '<>')
->execute();
$this
->assertTrue($this
->performUpgrade(), 'The upgrade was completed successfully.');
// Check if locale_update_8005() is succesfully completed by checking
// whether index 'plural' has been removed.
$this
->assertFalse(db_index_exists('locales_target', 'plural'), 'Translations without plurals upgraded.');
}