public function testFileDelete()
 {
     $prophecy = $this->prophesize('League\\Flysystem\\FilesystemInterface');
     $prophecy->delete('path.txt')->willReturn(true);
     $filesystem = $prophecy->reveal();
     $file = new File(null, 'path.txt');
     $file->setFilesystem($filesystem);
     $output = $file->delete();
     $this->assertTrue($output);
 }