assertEquals( 1, root.getMutableChildren( "child2" ).length );
assertTrue( root.getMutableChildren( "child1" )[0] == root.getChild( "child1" ) );
// Add an immutable child.
DefaultConfiguration immutableChild = new DefaultConfiguration( "immutable-child", "-" );
immutableChild.makeReadOnly();
try
{
immutableChild.setAttribute( "attr", "attr" );
fail( "Read-only DefaultConfiguration wasn't read-only!" );