Runs the test case.
Document doc;
Node newNode;
String newValue;
doc = (Document) load("staff", true);
newNode = doc.createProcessingInstruction("TARGET", "DATA");
newValue = newNode.getNodeValue();
assertEquals("initial", "DATA", newValue);
newNode.setNodeValue("This should have an effect");
newValue = newNode.getNodeValue();
assertEquals("after", "This should have an effect", newValue);