code: /** 
   * Asserts  {@link ExternalContextsNavigableSet#getParentExternalContext(ServiceName)}
   * @throws Exception
   */
  @Test public void testGetParentContext() throws Exception {
    final ServiceName nameA=ServiceName.JBOSS.append("a");
    final ServiceName nameP=ServiceName.JBOSS.append("p");
    final ServiceName namePC=ServiceName.JBOSS.append("p","c");
    final ServiceName nameZ=ServiceName.JBOSS.append("z");
    ExternalContextsNavigableSet set=new ExternalContextsNavigableSet();
    set.addExternalContext(nameP);
    assertNull(set.getParentExternalContext(nameA));
    assertNull(set.getParentExternalContext(nameP));
    assertNotNull(set.getParentExternalContext(namePC));
    assertEquals(nameP,set.getParentExternalContext(namePC));
    assertNull(set.getParentExternalContext(nameZ));
  }
  