### Question:
IdentifierImpl implements Identifier { public static Identifier gensym(String pfx) { UUID uuid = UUID.randomUUID(); return new IdentifierImpl(pfx + ":" + uuid.toString()); } IdentifierImpl(URI uriIn);  IdentifierImpl(String idIn);  IdentifierImpl(Identifier identifierBase, String id); static Identifier gensym(String pfx); static Identifier gensym(); @Override URI getUri(); @Override String toString(); @Override boolean equals(Object obj); @Override int hashCode(); @Override String stringValue();  }### Answer:
@Test public void testGensym() { assertNotNull(IdentifierImpl.gensym()); }