Confirms an item removal from a feed.
\Drupal\aggregator\Plugin\Core\Entity\Feed $feed: Feed object representing the feed.
function removeFeedItems(Feed $feed) {
$this
->drupalPost('admin/config/services/aggregator/remove/' . $feed
->id(), array(), t('Remove items'));
$this
->assertRaw(t('The news items from %title have been removed.', array(
'%title' => $feed
->label(),
)), 'Feed items removed.');
}