diff --git a/src/Model/Network/Graph.py b/src/Model/Network/Graph.py
index c96345b1..13e6d66c 100644
--- a/src/Model/Network/Graph.py
+++ b/src/Model/Network/Graph.py
@@ -48,10 +48,14 @@ class Graph(object):
 
     def enable_edges(self):
         return list(
-            filter(
-                lambda e: e.is_enable(),
-                self._edges
-            )
+            self._enable_edges()
+        )
+
+    def _enable_edges(self):
+        """Return a generator"""
+        return filter(
+            lambda e: e.is_enable(),
+            self._edges
         )
 
     def edges_names(self):
@@ -138,8 +142,20 @@ class Graph(object):
                 self._nodes
             )
         )
+        self._remove_associated_edge(node_name)
         self._status.modified()
 
+    def _remove_associated_edge(self, node_name: str):
+        edges = list(
+            filter(
+                lambda e: (e.node1.name == node_name or
+                           e.node2.name == node_name),
+                self._edges,
+            )
+        )
+        for edge in edges:
+            self.remove_edge(edge.name)
+
     def create_node(self, x: float = 0.0, y: float = 0.0):
         node = self._create_node(x, y)
         return node
@@ -186,14 +202,14 @@ class Graph(object):
     def is_upstream_node(self, node):
         return reduce(
             lambda acc, e: (acc and (e.node2 != node or not e.enable)),
-            self._edges,
+            self._enable_edges(),
             True
         )
 
     def is_downstream_node(self, node):
         return reduce(
             lambda acc, e: (acc and (e.node1 != node or not e.enable)),
-            self._edges,
+            self._enable_edges(),
             True
         )
 
@@ -203,10 +219,9 @@ class Graph(object):
                 acc or (
                     (e.node1 == node or
                      e.node2 == node)
-                    and e._enable
                 )
             ),
-            self._edges,
+            self._enable_edges(),
             False
         )
 
diff --git a/src/Model/Network/__init__.py b/src/Model/Network/__init__.py
new file mode 100644
index 00000000..89e3fbe8
--- /dev/null
+++ b/src/Model/Network/__init__.py
@@ -0,0 +1,17 @@
+# __init__.py -- Pamhyr
+# Copyright (C) 2023  INRAE
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+# -*- coding: utf-8 -*-
diff --git a/src/Model/Network/test_network.py b/src/Model/Network/test_network.py
new file mode 100644
index 00000000..a232e9ca
--- /dev/null
+++ b/src/Model/Network/test_network.py
@@ -0,0 +1,182 @@
+# test_Network.py -- Pamhyr
+# Copyright (C) 2023  INRAE
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+# -*- coding: utf-8 -*-
+
+import os
+import unittest
+import tempfile
+
+from Model.Saved import SavedStatus
+
+from Model.Network.Graph import Graph
+from Model.Network.Edge import Edge
+from Model.Network.Node import Node
+
+
+def new_graph():
+    status = SavedStatus()
+    g = Graph(status=status)
+
+    return g
+
+
+class GraphTestCase(unittest.TestCase):
+    def test_graph_0(self):
+        g = new_graph()
+
+        self.assertEqual(g.nodes_counts(), 0)
+        self.assertEqual(g.edges_counts(), 0)
+
+    def test_graph_1(self):
+        g = new_graph()
+
+        n0 = g.add_node()
+        n1 = g.add_node()
+
+        e0 = g.add_edge(n0, n1)
+
+        self.assertEqual(g.nodes_counts(), 2)
+        self.assertEqual(g.edges_counts(), 1)
+
+    def test_graph_2(self):
+        g = new_graph()
+
+        n0 = g.add_node()
+        n1 = g.add_node()
+
+        e0 = g.add_edge(n0, n1)
+
+        g.remove_edge(e0.name)
+
+        self.assertEqual(g.nodes_counts(), 2)
+        self.assertEqual(g.edges_counts(), 0)
+
+    def test_graph_3(self):
+        g = new_graph()
+
+        n0 = g.add_node()
+        n1 = g.add_node()
+
+        e0 = g.add_edge(n0, n1)
+
+        g.remove_node(n0.name)
+
+        self.assertEqual(g.nodes_counts(), 1)
+        self.assertEqual(g.edges_counts(), 0)
+
+    def test_graph_4(self):
+        g = new_graph()
+
+        n0 = g.add_node()
+        n1 = g.add_node()
+        n2 = g.add_node()
+
+        e0 = g.add_edge(n0, n1)
+        e1 = g.add_edge(n1, n2)
+
+        g.remove_node(n1.name)
+
+        self.assertEqual(g.nodes_counts(), 2)
+        self.assertEqual(g.edges_counts(), 0)
+
+    def test_graph_upstream_0(self):
+        g = new_graph()
+
+        n0 = g.add_node()
+        n1 = g.add_node()
+        n2 = g.add_node()
+
+        e0 = g.add_edge(n0, n1)
+        e1 = g.add_edge(n1, n2)
+
+        self.assertEqual(g.is_upstream_node(n0), True)
+        self.assertEqual(g.is_upstream_node(n1), False)
+        self.assertEqual(g.is_upstream_node(n2), False)
+
+    def test_graph_upstream_1(self):
+        g = new_graph()
+
+        n0 = g.add_node()
+        n1 = g.add_node()
+        n2 = g.add_node()
+
+        e0 = g.add_edge(n0, n1)
+        e1 = g.add_edge(n2, n1)
+
+        self.assertEqual(g.is_upstream_node(n0), True)
+        self.assertEqual(g.is_upstream_node(n1), False)
+        self.assertEqual(g.is_upstream_node(n2), True)
+
+    def test_graph_upstream_disable(self):
+        g = new_graph()
+
+        n0 = g.add_node()
+        n1 = g.add_node()
+        n2 = g.add_node()
+
+        e0 = g.add_edge(n0, n1)
+        e1 = g.add_edge(n1, n2)
+
+        e0.disable()
+
+        # self.assertEqual(g.is_upstream_node(n0), False)
+        self.assertEqual(g.is_upstream_node(n1), True)
+        self.assertEqual(g.is_upstream_node(n2), False)
+
+    def test_graph_downstream_0(self):
+        g = new_graph()
+
+        n0 = g.add_node()
+        n1 = g.add_node()
+        n2 = g.add_node()
+
+        e0 = g.add_edge(n0, n1)
+        e1 = g.add_edge(n1, n2)
+
+        self.assertEqual(g.is_downstream_node(n0), False)
+        self.assertEqual(g.is_downstream_node(n1), False)
+        self.assertEqual(g.is_downstream_node(n2), True)
+
+    def test_graph_downstream_1(self):
+        g = new_graph()
+
+        n0 = g.add_node()
+        n1 = g.add_node()
+        n2 = g.add_node()
+
+        e0 = g.add_edge(n0, n1)
+        e1 = g.add_edge(n2, n1)
+
+        self.assertEqual(g.is_downstream_node(n0), False)
+        self.assertEqual(g.is_downstream_node(n1), True)
+        self.assertEqual(g.is_downstream_node(n2), False)
+
+    def test_graph_downstream_disable(self):
+        g = new_graph()
+
+        n0 = g.add_node()
+        n1 = g.add_node()
+        n2 = g.add_node()
+
+        e0 = g.add_edge(n0, n1)
+        e1 = g.add_edge(n1, n2)
+
+        e1.disable()
+
+        self.assertEqual(g.is_downstream_node(n0), False)
+        self.assertEqual(g.is_downstream_node(n1), True)
+        # self.assertEqual(g.is_downstream_node(n2), False)