### Question:
IdentifierImpl implements Identifier { @Override public String toString() { return this.stringValue(); } 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 testIdentifierImplString() { URI uri = URI.create("com:test"); Identifier id = new IdentifierImpl(uri.toString()); assertEquals(uri.toString(), id.toString()); }
@Test public void testIdentifierImplIdentifierString() { URI uri = URI.create("com:test"); Identifier id1 = new IdentifierImpl(uri); Identifier id = new IdentifierImpl(id1, "junit"); assertEquals("com:test:junit", id.toString()); }
@Test public void testToString() { URI uri = URI.create("com:test"); Identifier id1 = new IdentifierImpl(uri); assertTrue(id1.toString().startsWith("com:test")); }