public static  void main(String[] args) 
{
        TestRunner.run(SetContentTest.class);
}

 public  void testDocument() throws Exception 
{
        document.setName("doc1");
        Element oldRoot = document.getRootElement();
        assertTrue("Current root has document",
                oldRoot.getDocument() == document);
        Document doc2 = DocumentHelper.createDocument();
        doc2.setName("doc2");
        assertTrue("Doc2 has no root element", doc2.getRootElement() == null);
        doc2.setContent(document.content());
        Element newRoot = doc2.getRootElement();
        assertTrue("Current root has document",
                oldRoot.getDocument() == document);
        assertTrue("Doc2 has now has root element", newRoot != null);
        assertTrue("Doc2 has different root element", newRoot != oldRoot);
        assertTrue("Root element now has document",
                newRoot.getDocument() == doc2);
        testParent(doc2.getRootElement());
        testDocument(doc2, doc2);
        doc2.clearContent();
        assertTrue("New Doc has no root", doc2.getRootElement() == null);
        assertTrue("New root has no document", newRoot.getDocument() == null);
}

 protected  void testDocument(Branch branch,
    Document doc) 
{
        for (int i = 0, size = branch.nodeCount(); i <  size; i++) {
            Node node = branch.node(i);
            assertTrue("Node has correct document", node.getDocument() == doc);
        }
}

Tests all the children of the branch have the correct document

 protected  void testParent(Branch parent) 
{
        for (int i = 0, size = parent.nodeCount(); i <  size; i++) {
            Node node = parent.node(i);
            assertTrue("Child node of root has parent of root", node
                    .getParent() == parent);
        }
}

Tests all the children of the branch have the correct parent

 public  void testRootElement() throws Exception 
{
        Document doc3 = DocumentHelper.createDocument();
        doc3.setName("doc3");
        Element root = doc3.addElement("root");
        Element oldElement = root.addElement("old");
        assertTrue("Doc3 has root element", root != null);
        root.setContent(document.getRootElement().content());
        assertTrue("Doc3's root now has content", root.nodeCount()  > 0);
        assertTrue("Old element has no parent now",
                oldElement.getParent() == null);
        assertTrue("Old element has no document now",
                oldElement.getDocument() == null);
        testParent(root);
        testDocument(root, doc3);
}