public function testLookupDeferred()
{
$body = json_decode(file_get_contents(__DIR__ . '/../fixtures/datastore/entity-batch-lookup.json'), true);
$this->connection->lookup(Argument::any())->willReturn(['deferred' => [$body[0]['entity']['key']]]);
$this->operation->setConnection($this->connection->reveal());
$key = $this->operation->key('Kind', 'ID');
$res = $this->operation->lookup([$key]);
$this->assertTrue(is_array($res));
$this->assertTrue(isset($res['deferred']) && is_array($res['deferred']));
$this->assertInstanceOf(Key::class, $res['deferred'][0]);
}