code: func (m *MockFileSystem) Copy(arg0 io.Writer, arg1 io.Reader) (int64, error) {
  	ret := m.ctrl.Call(m, "Copy", arg0, arg1)
  	ret0, _ := ret[0].(int64)
  	ret1, _ := ret[1].(error)
  	return ret0, ret1
  }
docs: // Copy mocks base method