This tests that various combinations of replaceChild on the document works as specified. If this test succeeds, there will be a number of "SUCCESS" lines below followed by "SUCCESS - All tests succeeded".
replacing element with element
SUCCESS: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"><bar/>
replacing element with doctype
SUCCESS: <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
SUCCESS - All tests succeeded!