### Question:
TokenFilter { public void addReturnAttribute(CoreTokenField field) { Reject.ifNull(field); returnFields.add(field); } TokenFilter(); QueryFilter<CoreTokenField> getQuery(); void setQuery(QueryFilter<CoreTokenField> query); Set<CoreTokenField> getReturnFields(); void addReturnAttribute(CoreTokenField field); String toString();  }### Answer:
@Test (expectedExceptions = NullPointerException.class) public void shouldPreventNullReturnAttribute() { filter.addReturnAttribute(null); }