Laravel单元测试scandir失败，因为基本路径错误

Question

I have a controller that gets list of images from folders and passes them to the view:

public function create()
{
    $marker_images = scandir("./img/markers");
    $background_images = scandir("./img/backgrounds");
    $type = new Type();
    return view('admin.types.create',compact('type','marker_images','background_images'));
}

This works fine until i run my unit test, which then fails on the scandir step with

failed to open dir: No such file or directory

if I add

exec('pwd',$return);
    print_r($return);

I see that the path is changing, when i manually vist the page the path is

/Users/<my username>/Sites/core-site/public 

but when the unit test is executed

/Users/<my username>/Sites/core-site

how do I get it to pick the correct base path for the unit test?

my unit test looks like this:

public function testTypesCreate()
{

    $controller = $this->app->make('App\Http\Controllers\Admin\TypeController');
    $response = $controller->create();
    $this->assertEquals($response->name(), 'admin.types.create');

}