@Test
 public void remove_A$String() throws Exception {
   MemcachedSessionStore store = new MemcachedSessionStore(getMemcached());
   // given
   String key = "MemcachedSessionStoreTest#remove_A$String_" + System.currentTimeMillis();
   // when
   store.set(key, 60, "aaa");
   store.remove(key);
   String actual = store.get(key);
   // then
   assertThat(actual, is(nullValue()));
 }