Amphp and mocking

WriteIO

<?php

require __DIR__ . '/../vendor/autoload.php';

use Amp\Http\Client\HttpClientBuilder;
use Amp\Http\Client\Request;
use Amp\Loop;
use Amp\ByteStream\ClosedException;
use Amp\File;

interface IO extends Amp\Promise
{
    // IO must be comparable to be able to test it
    public function equals(IO $io);
}

class WriteIO implements IO
{
    private $message;
    private $handle;

    public function __construct($handle, $message)
    {
        $this->message = $message;
        $this->handle = $handle;
    }

    public function onResolve($onResolved)
    {
        $this->handle->write($this->message)->onResolve($onResolved);
    }

    public function equals(IO $io)
    {
        return $io->message === $this->message;
    }
}

class FileSaver
{
    private $logger;
    private $httpClient;

    public function __construct($logger, $httpClient)
    {
        $this->logger = $logger;
        $this->httpClient = $httpClient;
    }

    public function saveFile($path, $file)
    {
        $logger = $this->logger;
        yield new WriteIO($logger, 'Saving file ' . $path);
        $request = new Request('https://cloudfiles.fooservice.com/', 'POST');
        $request->setBody($file);
        $response = yield $this->httpClient->request($request);
        if ($response->getStatus() === 200) {
            yield new WriteIO($logger, 'Successfully saved file ' . $path);
        } else {
            $msg = 'Failed to save file ' . $path;
            yield new WriteIO($logger, $msg);
            throw new Exception($msg);
        }
    }
}

Loop::run(function() {
    $httpClient = HttpClientBuilder::buildDefault();
    $logger = yield File\open('log.txt', "c+");
    $fileSaver = new FileSaver($logger, $httpClient);
    
    // Comment out live run.
    //yield from $fileSaver->saveFile('moo', 0);
    //return;

    // List of effects expected by saveFile()
    $effects = [
        [
            'yield' => new WriteIO(null, 'Saving file moo'),
            'send' => null
        ],
        [
            'yield' => null,
            'send' => new class { public function getStatus() { return 200; } }
        ]
    ];
    $gen = $fileSaver->saveFile('moo', 0);
    testGenerator($gen, $effects);
});

function testGenerator($gen, $effects)
{
    // Loop all effects and make sure they correspond to expectations.
    foreach ($gen as $i => $promise) {
        if ($effects[$i]['yield']) {
            if (!$promise->equals($effects[$i]['yield'])) {
                throw new Exception('Failed test');
            }
        }
        if ($effects[$i]['send']) {
            $gen->send($effects[$i]['send']);
        }
    }
}