LinkedProperties extends Properties { @Override public synchronized void clear() { linkMap.clear(); }  @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 clearTest() { linkedProperties.put("key", "value"); linkedProperties.clear(); assertThat(linkedProperties.entrySet().size(), is(0)); }