public function testFallbackWhenNotSupported()
{
$request = new Request();
$request->setRequestFormat('html');
$format = ErrorFormatGuesser::guessErrorFormat($request, ['xml' => ['text/xml'], 'jsonld' => ['application/ld+json', 'application/json']]);
$this->assertEquals('xml', $format['key']);
$this->assertEquals('text/xml', $format['value'][0]);
}