Confirm that an extended query has a "tag" added to it.
function testExtenderHasTag() {
$query = db_select('test')
->extend('SelectQueryExtender');
$query
->addField('test', 'name');
$query
->addField('test', 'age', 'age');
$query
->addTag('test');
$this
->assertTrue($query
->hasTag('test'), 'hasTag() returned true.');
$this
->assertFalse($query
->hasTag('other'), 'hasTag() returned false.');
}