public PatchTree generatePatchTree()
  {
    try
    {
      return new PatchTree( _patchTree.getDataMap().copy());
    }
    catch (CloneNotSupportedException e)
    {
      throw new IllegalStateException("Error copying data map: " + _patchTree.getDataMap(), e);
    }
  }
@Test
  public void testEmptyPatch()
  {
    PatchTreeRecorder<PatchTreeTestModel> pc = makeOne();
    Assert.assertEquals(pc.generatePatchTree().getDataMap(), new DataMap());
  }