private void MusicSaveButton_Click(object sender, RoutedEventArgs e)
        {
            if (textBoxSinger.Text != "" && textBoxSongTitle.Text != "")
            {
                if (_activeController.Selected == null)
                {
                    var newSong = new Song()
                    {
                        Singer = textBoxSinger.Text,
                        Title  = textBoxSongTitle.Text,
                        File   = _newFile
                    };

                    _activeController.AddMedia(newSong);
                }
                else
                {
                    var selectedSong = (Song)_activeController.Selected;

                    if (_newFile == null)
                    {
                        _newFile = selectedSong.File;
                    }

                    selectedSong.Singer = textBoxSinger.Text;
                    selectedSong.Title  = textBoxSongTitle.Text;
                    selectedSong.File   = _newFile;

                    _activeController.UpdateMedia(selectedSong);
                }

                _activeController.ClearSelected();
                textBoxSinger.Text    = "";
                textBoxSongTitle.Text = "";
                checkBoxMusicFilePresent.IsChecked = false;

                musicListBox.Items.Refresh();
            }
            else
            {
                MessageBox.Show("Please fill in all the fields");
            }
        }
        public void AddMedia_ShouldAddMediaItem()
        {
            // Arrange
            _sut = new TestMediaController();
            Song song = new Song();

            // Act
            _sut.AddMedia(song);

            // Assert
            Assert.IsTrue(_sut.List.Contains(song));
        }