public function testGuessExtension()
{
$file = new File($this->root . '/test.gif');
$this->assertEquals('gif', $file->guessExtension());
$file = new File($this->root . '/test');
$this->assertEquals('gif', $file->guessExtension());
$file = new File($this->root . '/other-file.example');
$this->assertNull($file->guessExtension());
$file = new File($this->root . '/.unknownextension');
$this->assertEquals('bin', $file->guessExtension());
}
