Do not crash with binary response body

This is needed to simulate e.g. gzip response without having to override the `getRef` method.

Author: jtojnar

src/Response.php

@@ -24,7 +24,7 @@ public function __construct( string $body, array $headers = [], int $status = 20
 
 public function getRef() : string {
 $content = json_encode([
-$this->body,
+md5($this->body),
 $this->status,
 $this->headers,
 ]);

test/Integration/MockWebServer_IntegrationTest.php

@@ -251,6 +251,21 @@ public function testEmptySingle() : void {
 $this->assertSame('', file_get_contents($url));
 }
 
+public function testBinaryResponse() : void {
+$response = new Response(
+gzencode('This is our http body response'),
+[ 'Content-Encoding: gzip' ],
+200
+);
+
+$url = self::$server->setResponseOfPath('/', $response);
+$content = @file_get_contents($url);
+
+$this->assertNotFalse($content);
+$this->assertSame('This is our http body response', gzdecode($content));
+$this->assertContains('Content-Encoding: gzip', $http_response_header);
+}
+
 /**
  * @dataProvider requestInfoProvider
  */