Laravel:用真实文件测试post

我在用拉维 5.6 post 需要 file . 所以我写的

$file = new \Illuminate\Http\UploadedFile(base_path() . '/tests/samples/Cylinder.stl', 'Cylinder.stl');

$response = $this->post( route('attachments.store' ) , [
    'file' => $file,
    'attachable_id' => $this->threedviews->id,
    'attachable_type' => 'App\ThreeDView',
]);

dd( $this->app['session.store'] ) ,我明白了

#bags: array:1 [
        "default" => Illuminate\Support\MessageBag {#1198
          #messages: array:1 [
            "file" => array:1 [
              0 => "The file failed to upload."
            ]
          ]
          #format: ":message"
        }
      ]

当我手动使用表格时,一切都很好。 $file 看起来很奇怪

Illuminate\Http\UploadedFile {#43
  -test: false
  -originalName: "Cylinder.stl"
  -mimeType: "application/octet-stream"
  -error: 0
  ...
}

test 旗子被设为假,应该是这样吗?