测试存储时创建的假文件

Question

我有一个用于测试上传功能的课程：

class FileUploadTest extends TestCase
{

    protected $currentDate;
    protected $filename;

    public function setUp() {
        parent::setUp();
        $this->currentDate = now()->toDateString();
        $this->filename = str_random(20) . '.jpg';
        Storage::fake('uploads');
    }

    /** @test */
    public function test_a_user_can_upload_a_file() {
        $res = $this->json('POST', '/files', [
            'file' => UploadedFile::fake()->image($this->filename)
        ]);
        $content = $res->decodeResponseJson();

        Storage::assertExists($content['path']);
    }

...
}

$content['path']有这种格式：'uploads/2018-06-06/filename.ext'

我看到每次测试后，都会在storage/app文件夹中创建假文件。我该如何阻止它？