public void testAddHousehold_DuplicateId(){
HouseholdsImpl hhs = new HouseholdsImpl();
Household hh1 = new HouseholdImpl(Id.create("1", Household.class));
Household hh2 = new HouseholdImpl(Id.create("1", Household.class));
assertEquals("Shouldn't have a household.", 0, hhs.getHouseholds().size());
hhs.addHousehold(hh1);
assertEquals("Didn't add the household.", 1, hhs.getHouseholds().size());
assertEquals("Should have added the household.", hh1, hhs.getHouseholds().get(hh1.getId()));
try{
hhs.addHousehold(hh2);
fail("Should not have accepted household with similar Id.");
} catch (IllegalArgumentException e){
}
}