diff --git a/tests/test_core.py b/tests/test_core.py
index 2e88bdd..6ea62dd 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -34,6 +34,7 @@ def test_rhu_formatting(thermostat_type_1):
     assert('rhu1_less05F' == thermostat_type_1._format_rhu('rhu1', -np.inf, 5, None))
     assert('rhu1_greater55F' == thermostat_type_1._format_rhu('rhu1', 55, np.inf, None))
     assert('rhu1_30F_to_45F' == thermostat_type_1._format_rhu('rhu1', 30, 45, None))
+    assert('rhu2_05F_to_10F_aux_duty_cycle' == thermostat_type_1._format_rhu('rhu2', 5, 10, 'aux_duty_cycle'))