diff --git a/tests/test_network.py b/tests/test_network.py
index 2e5ec31..7d9d971 100644
--- a/tests/test_network.py
+++ b/tests/test_network.py
@@ -386,20 +386,27 @@ def test_inconsistent_time_coords(input_output, wrong_length):
         Network([wind, electricity, demand])
 
 
-@pytest.mark.parametrize("missing_size_commodity", [False, True])
-def test_multiple_commodities_chp_power_plant(missing_size_commodity):
+@pytest.mark.parametrize("error", [None, "missing_size_commodity", "storage_not_allowed"])
+def test_multiple_commodities_chp_power_plant(error):
     time_coords_num = 10
+    storage = Storage(
+        costs=10 * ureg.EUR / ureg.MWh,
+        max_charging_speed=0.1,
+        storage_loss=0.1,
+        charging_loss=0.0,
+    )
     chp_power_plant = Node(
         name="chp_power_plant",
         inputs=[],
         input_commodities=["gas"],
         costs=3 * ureg.EUR / ureg.MW,
         input_flow_costs=10 * ureg.EUR / ureg.t,
-        size_commodity=None if missing_size_commodity else "electricity",
+        size_commodity=None if error == "missing_size_commodity" else "electricity",
         convert_factors={
             "electricity": ("gas", 2 / (ureg.t / ureg.h) * ureg.MW),
             "heat": ("gas", 4 / (ureg.t / ureg.h) * ureg.MW),
         },
+        storage=storage if error == "storage_not_allowed" else None,
     )
     electricity_demand = NodeFixOutput(
         name="electricity_demand",
@@ -426,7 +433,7 @@ def test_multiple_commodities_chp_power_plant(missing_size_commodity):
         time_coords_num=time_coords_num,
     )
 
-    if missing_size_commodity:
+    if error == "missing_size_commodity":
         # if a node has multiple ouptut commodities, size_commodity should be set
         msg = (
             "node 'chp_power_plant': missing size_commodity parameter, but required for "
@@ -434,6 +441,10 @@ def test_multiple_commodities_chp_power_plant(missing_size_commodity):
         )
         with pytest.raises(ValueError, match=msg):
             _ = Network(**network_parmas)
+    elif error == "storage_not_allowed":
+        msg = "storage not supported for multiple output commodities"
+        with pytest.raises(ValueError, match=msg):
+            _ = Network(**network_parmas)
     else:
         network = Network(**network_parmas)
 
diff --git a/tests/test_node.py b/tests/test_node.py
index 0610748..4147274 100644
--- a/tests/test_node.py
+++ b/tests/test_node.py
@@ -1,6 +1,12 @@
 import pytest
 
-from syfop.node import Node, NodeScalableInput
+from syfop.node import (
+    Node,
+    NodeFixOutput,
+    NodeScalableInput,
+    NodeScalableOutput,
+    Storage,
+)
 from syfop.units import ureg
 from syfop.util import const_time_series
 
@@ -95,3 +101,29 @@ def test_wrong_node_input():
             input_commodities="electricity",
             costs=0,
         )
+
+
+def test_scalable_output_not_implemented():
+    # this unit test is a bit useless, but it increases coverage
+    error_msg = "NodeScalableOutput is not implemented yet"
+    with pytest.raises(NotImplementedError, match=error_msg):
+        NodeScalableOutput()
+
+
+def test_storage_forbidden_for_output_nodes():
+    storage = Storage(
+        costs=10 * ureg.EUR / ureg.MWh,
+        max_charging_speed=1.0,
+        storage_loss=0.0,
+        charging_loss=0.0,
+    )
+
+    error_msg = "storage is not supported for output nodes"
+    with pytest.raises(NotImplementedError, match=error_msg):
+        _ = NodeFixOutput(
+            name="demand",
+            inputs=[],
+            input_commodities="electricity",
+            output_flow=const_time_series(5.0) * ureg.kW,
+            storage=storage,
+        )