public void guiTestDocumentSwap() throws Exception {
final JTextField textField = new JTextField();
final AbstractDocument documentA = (AbstractDocument) textField.getDocument();
documentA.insertString(0, "documentA", null);
final AbstractDocument documentB = new PlainDocument();
documentB.insertString(0, "documentB", null);
final int originalDocumentAListenerCount = documentA.getDocumentListeners().length;
final int originalDocumentBListenerCount = documentB.getDocumentListeners().length;
// using the textField in a TextComponentMatcherEditor will install a DocumentListener