### Question:
WorkflowNamespaceContext implements NamespaceContext { public String getNamespaceURI(String prefix) { if (prefix == null) throw new NullPointerException("Null prefix"); else if ("t".equals(prefix)) return "http: else if ("xml".equals(prefix)) return XMLConstants.XML_NS_URI; return XMLConstants.NULL_NS_URI; }  String getNamespaceURI(String prefix); String getPrefix(String uri); Iterator getPrefixes(String uri);  }### Answer:
@Test public void testGetNamespaceURI() { WorkflowNamespaceContext instance = new WorkflowNamespaceContext(); String result; try { result = instance.getNamespaceURI(null); fail("Should raise exception"); } catch (NullPointerException ex) { } result = instance.getNamespaceURI("t"); assertEquals("http: result = instance.getNamespaceURI("xml"); assertEquals(XMLConstants.XML_NS_URI, result); result = instance.getNamespaceURI(""); assertEquals(XMLConstants.NULL_NS_URI, result); }