Ensure get multiple values propagation to previous backends.
public function testGetMultipleHasPropagated() {
$cids = array(
't3',
't23',
);
$this->chain
->getMultiple($cids);
$cached = $this->firstBackend
->get('t3');
$this
->assertNotIdentical(FALSE, $cached, 'Test 3 has been propagated to the first backend');
$this
->assertIdentical(33, $cached->data, 'And value has been kept');
$cached = $this->secondBackend
->get('t3');
$this
->assertNotIdentical(FALSE, $cached, 'Test 3 has been propagated to the second backend');
$this
->assertIdentical(33, $cached->data, 'And value has been kept');
$cached = $this->firstBackend
->get('t23');
$this
->assertNotIdentical(FALSE, $cached, 'Test 2 has been propagated to the first backend');
$this
->assertIdentical(232, $cached->data, 'And value has been kept');
}