GuzzleHttp\Tests\ClientTest::testCanAddJsonData PHP Method

    public function testCanAddJsonData()
    {
        $mock = new MockHandler([new Response()]);
        $client = new Client(['handler' => $mock]);
        $request = new Request('PUT', 'http://foo.com');
        $client->send($request, ['json' => ['foo' => 'bar']]);
        $last = $mock->getLastRequest();
        $this->assertEquals('{"foo":"bar"}', (string) $mock->getLastRequest()->getBody());
        $this->assertEquals('application/json', $last->getHeaderLine('Content-Type'));
    }