title: How can I test a private or fileprivate function in project
body: <p>I want to write some unit testing code for a manager class, the function I would write for is using some small <code>private</code> functions. I will prepare a lot if I testing the <code>public</code> function, so I want to test those <code>private</code> functions. But in test target I can't call the private function directly.</p>
  
  <p>So I wanna ask, is there's a way to test them without change them from <code>private</code> to <code>internal</code> or <code>public</code>?</p>