public function testOperation()
{
$opName = 'testOperation';
$snippet = $this->snippetFromMethod(SpeechClient::class, 'operation');
$snippet->addLocal('speech', $this->client);
$snippet->addLocal('operationName', $opName);
$res = $snippet->invoke('operation');
$this->assertInstanceOf(Operation::class, $res->returnVal());
$this->assertEquals($opName, $res->returnVal()->name());
}