Delete an aggregator feed.
$feed: Feed object representing the feed.
function deleteFeed($feed) {
$this
->drupalPost('admin/config/services/aggregator/edit/feed/' . $feed->fid, array(), t('Delete'));
$this
->assertRaw(t('The feed %title has been deleted.', array(
'%title' => $feed->title,
)), 'Feed deleted successfully.');
}