LinkedProperties extends Properties { @Override public Set<Map.Entry<Object, Object>> entrySet() { return linkMap.entrySet(); }  @Override synchronized Object put(Object key, Object value); @Override synchronized boolean contains(Object value); @Override boolean containsValue(Object value); @Override synchronized Enumeration<Object> elements(); @Override Set<Map.Entry<Object, Object>> entrySet(); @Override synchronized void clear(); @Override synchronized boolean containsKey(Object key);  }
@Test public void entrySetTest() { linkedProperties.put("key", "value"); linkedProperties.put("key2", "value2"); assertThat(linkedProperties.entrySet().size(), is(2)); }