### Question:
Tags implements Serializable { public int size() { return ts.size(); } Tags();  Tags(String tags);  Tags(String... tags); void setTags(String tags); boolean add(String t); boolean remove(String t); boolean contains(String t); Iterator<String> iterator(); int size(); boolean containsAll(Tags tags); boolean containsAny(Tags tags); @Override String toString(); @Override boolean equals(Object o); @Override int hashCode();  }### Answer:
@Test public void testNullTags() { Tags ts = new Tags((String) null); assertEquals(0, ts.size(), "size=0"); assertEquals(new Tags(), ts, "empty tags"); assertEquals(new Tags(""), ts, "empty tags \"\""); assertEquals(new Tags(" "), ts, "empty tags (blank)"); }