### Question:
GroupsThreadStore { public static void storeGroups(AccessGroupSet groups) { GroupsThreadStore.groups.set(groups); if (groups != null) { GroupsThreadStore.groupString.set(groups.joinAccessGroups(";")); GroupsThreadStore.agentPrincipals.remove(); } }  static void storeGroups(AccessGroupSet groups); static AccessGroupSet getGroups(); static String getGroupString(); static void clearGroups(); static void storeUsername(String username); static String getUsername(); static void storeEmail(String email); static String getEmail(); static AgentPrincipals getAgentPrincipals(); static void clearUsername(); static void clearStore();  }### Answer:
@Test public void nullGroupsTest() { GroupsThreadStore.storeGroups(null); }