Testing drag-and-drop files onto application

I am looking for a method to perform a drag-and-drop of a file/multiple files onto my application from a unit test. For example selecting some files in Windows Explorer, drag them and drop them on my application.

I am capable of testing drag-and-drop behavior between two components in my application (see below - feel free to indicate if you know a better way), but I have no idea how to do the same when the data has to come from outside my application.

I thought about using the debugger to inspect a 'file' Transferable when I do the drag-and-drop operation by hand, but there must be a better way then hard-coding a complete Transferable.

Example of a drag-and-drop test between components

import org.junit.Test;

import javax.swing.Action;
import javax.swing.JTextField;
import javax.swing.TransferHandler;
import java.awt.event.ActionEvent;

import static org.junit.Assert.assertEquals;

public class DragAndDropTest {
  @Test
  public void dragAndDropBetweenTwoTextFields() {
    JTextField firstField = new JTextField();
    JTextField secondField = new JTextField();
    String testText = "Test text";
    firstField.setText( testText );
    firstField.selectAll();
    Action copyAction = TransferHandler.getCopyAction();
    copyAction.actionPerformed( new ActionEvent( firstField, ActionEvent.ACTION_PERFORMED, "Copy" ) );
    Action pasteAction = TransferHandler.getPasteAction();
    pasteAction.actionPerformed( new ActionEvent( secondField, ActionEvent.ACTION_PERFORMED, "Paste" ) );
    assertEquals( "Text is not copied", testText, secondField.getText() );
  }
}

Edit

Based on the comments under this question, I have updated my code snippet to 'fake' a drag-and-drop by providing a hard-coded Transferable. The code also contains a little main program which just creates an empty frame on which you can drop files. The path will then be printed on the console.

On my PC, drag-and-drop of a file does not use the javaFileListFlavor but the URI flavor. Previous experiences (see this question) already teached me that the Transferable a component receives when dragging something from outside the Java application might differ in subtle ways.

So to be completely clear: I want to test the part of my code that extracts the information from the received Transferable. The 'information-handling' code (e.g. what happens when the application receives the file) can easily be tested without bothering with D&D. I just need to make sure I extract the correct information from the Transferable, and it is silly to test this with a hard-coded Transferable.

import org.junit.Test;

import javax.swing.Action;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.TransferHandler;
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.datatransfer.Clipboard;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.awt.event.ActionEvent;
import java.io.File;
import java.io.IOException;
import java.util.List;

import static org.junit.Assert.assertEquals;

public class DragAndDropTest {
  private static DataFlavor URI_LIST_FLAVOR = null;
  static {
    try {
      URI_LIST_FLAVOR = new DataFlavor( "text/uri-list;class=java.lang.String" );
    }
    catch ( ClassNotFoundException ignore ) {
    }
  }

  @Test
  public void testFileDragAndDrop() throws IOException, UnsupportedFlavorException {
    JComponent testComponent = new JPanel();
    TestingTransferHandler transferHandler = new TestingTransferHandler();
    testComponent.setTransferHandler( transferHandler );
    Clipboard clipBoard = new JLabel(  ).getToolkit().getSystemClipboard();
    Transferable transferable = new Transferable() {
      @Override
      public DataFlavor[] getTransferDataFlavors() {
        return new DataFlavor[]{URI_LIST_FLAVOR};
      }

      @Override
      public boolean isDataFlavorSupported( DataFlavor flavor ) {
        return flavor == URI_LIST_FLAVOR;
      }

      @Override
      public Object getTransferData( DataFlavor flavor ) throws UnsupportedFlavorException, IOException {
        if ( flavor == URI_LIST_FLAVOR ) {
          return new String( "file:///home/robins/Desktop/swingx-1.0-javadoc.jar" );
        }
        throw new UnsupportedFlavorException( flavor );
      }
    };
    clipBoard.setContents( transferable, null );
    Action pasteAction = TransferHandler.getPasteAction();
    pasteAction.actionPerformed( new ActionEvent( testComponent, ActionEvent.ACTION_PERFORMED, "Paste" ) );
    assertEquals( transferable.getTransferData( URI_LIST_FLAVOR ), transferHandler.transferable.getTransferData( URI_LIST_FLAVOR ) );
  }

  private static class TestingTransferHandler extends TransferHandler{
    public Transferable transferable;
    @Override
    public boolean canImport( TransferSupport support ) {
      return true;
    }
    @Override
    public boolean importData( TransferSupport support ) {
      transferable = support.getTransferable();
      try{
        if ( transferable.isDataFlavorSupported( DataFlavor.javaFileListFlavor ) ) {
          System.out.println("File list flavor");
          List<File> fileList = ( List<File> ) transferable.getTransferData( DataFlavor.javaFileListFlavor );
          System.out.println( "fileList = " + fileList );
        }
        if ( transferable.isDataFlavorSupported( URI_LIST_FLAVOR )){
          System.out.println("URI list flavor");
          String uriList = ( String ) transferable.getTransferData( URI_LIST_FLAVOR );
          System.out.println( "uriList = " + uriList );
        }
        return true;
      } catch ( UnsupportedFlavorException e ) {
        return false;
      } catch ( IOException e ) {
        return false;
      }
    }
  }

  public static void main( String[] args ) {
    EventQueue.invokeLater( new Runnable() {
      @Override
      public void run() {
        JFrame frame = new JFrame( "TestFrame" );
        JPanel contentPane = new JPanel( new BorderLayout(  ) );
        contentPane.setTransferHandler( new TestingTransferHandler() );
        frame.setContentPane( contentPane );
        frame.setSize( 200,200 );
        frame.setVisible( true );
        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
      }
    } );
  }
}