public function testPostStringBody()
{
$uri = 'http://httpbin.org/post';
$client = new Client();
$body = 'zanzibar';
$request = (new Request())->setUri($uri)->setMethod('POST')->setBody($body);
$promise = $client->request($request);
$response = \Amp\wait($promise);
$this->assertInstanceOf('Amp\\Artax\\Response', $response);
$result = json_decode($response->getBody());
$this->assertEquals($body, $result->data);
}