Test that we can attach meta data to a query object.
This is how we pass additional context to alter hooks.
function testMetaData() {
$query = db_select('test');
$query
->addField('test', 'name');
$query
->addField('test', 'age', 'age');
$data = array(
'a' => 'A',
'b' => 'B',
);
$query
->addMetaData('test', $data);
$return = $query
->getMetaData('test');
$this
->assertEqual($data, $return, 'Corect metadata returned.');
$return = $query
->getMetaData('nothere');
$this
->assertNull($return, 'Non-existent key returned NULL.');
}