@Test
public void test_less_null() {

  FunctionExpression less = dsl.less(DSL.literal(1),
      DSL.ref(INT_TYPE_NULL_VALUE_FIELD, INTEGER));
  assertEquals(BOOLEAN, less.type());
  assertEquals(LITERAL_NULL, less.valueOf(valueEnv()));
  less = dsl.less(DSL.ref(INT_TYPE_NULL_VALUE_FIELD, INTEGER), DSL.literal(1));
  assertEquals(BOOLEAN, less.type());
  assertEquals(LITERAL_NULL, less.valueOf(valueEnv()));
  less = dsl.less(DSL.ref(INT_TYPE_NULL_VALUE_FIELD, INTEGER),
      DSL.ref(INT_TYPE_NULL_VALUE_FIELD, INTEGER));
  assertEquals(BOOLEAN, less.type());
  assertEquals(LITERAL_NULL, less.valueOf(valueEnv()));
}