### Question:
DmDocument implements DmNode { @Override public String getStringValue() { throw new UnsupportedOperationException("getStringValue is not supported"); } DmDocument(final List<? extends DmNode> childAxis); @Override List<DmNode> getChildAxis(); @Override QName getName(); @Override String getStringValue();  }### Answer:
@Test(expected = UnsupportedOperationException.class) public void testGetStringValue() { DmDocument dmDocument = new DmDocument(new ArrayList<DmNode>()); dmDocument.getStringValue(); }