diff --git a/src/oemof/network/network/nodes.py b/src/oemof/network/network/nodes.py
index bc1e1e7..0a4b6c9 100644
--- a/src/oemof/network/network/nodes.py
+++ b/src/oemof/network/network/nodes.py
@@ -24,9 +24,18 @@ class Node(Entity):
     inputs: list or dict, optional
         Either a list of this nodes' input nodes or a dictionary mapping input
         nodes to corresponding inflows (i.e. input values).
+        List will be converted to dictionary with values set to None.
     outputs: list or dict, optional
         Either a list of this nodes' output nodes or a dictionary mapping
         output nodes to corresponding outflows (i.e. output values).
+        List will be converted to dictionary with values set to None.
+
+    Attributes
+    ----------
+    inputs: dict
+        A dictionary mapping input nodes to corresponding inflows.
+    outputs: dict
+        A dictionary mapping output nodes to corresponding outflows.
     """
 
     def __init__(self, *args, **kwargs):
diff --git a/tests/test_energy_system.py b/tests/test_energy_system.py
index 9af475e..6e602f5 100644
--- a/tests/test_energy_system.py
+++ b/tests/test_energy_system.py
@@ -42,6 +42,30 @@ def test_add_nodes(self):
         assert node2 in self.es.nodes
         assert (node1, node2) in self.es.flows().keys()
 
+    def test_add_flow_assignment(self):
+        assert not self.es.nodes
+
+        node0 = Node(label="node0")
+        node1 = Node(label="node1")
+        node2 = Node(label="node2", inputs={node0: Edge()})
+
+        self.es.add(node0, node1, node2)
+
+        assert (node0, node2) in self.es.flows().keys()
+        assert (node1, node2) not in self.es.flows().keys()
+        assert (node2, node1) not in self.es.flows().keys()
+
+        node2.inputs[node1] = Edge()
+
+        assert (node0, node2) in self.es.flows().keys()
+        assert (node1, node2) in self.es.flows().keys()
+        assert (node2, node1) not in self.es.flows().keys()
+
+        node2.outputs[node1] = Edge()
+        assert (node0, node2) in self.es.flows().keys()
+        assert (node1, node2) in self.es.flows().keys()
+        assert (node2, node1) in self.es.flows().keys()
+
     def test_that_node_additions_are_signalled(self):
         """
         When a node gets `add`ed, a corresponding signal should be emitted.