def test_remove_edge():
"""Test to remove an edge from the network."""
net = Network()
a = Node('a')
b = Node('b')
c = Node('c')
e = Edge(a, b, uid='e')
f = Edge(b, a, uid='f')
g = Edge(b, c, uid='g')
net.add_edge(e)
net.add_edge(f)
net.remove_edge(g)
assert net.number_of_edges() == 2
assert isinstance(net.edges['e'], Edge)
assert g not in net.edges
assert net.edges['a', 'b'] in net.edges
assert net.successors['a'] == {b}
assert net.outgoing['a'] == {e}
assert net.incident_edges['a'] == {e, f}
net.remove_edge(e)
assert net.number_of_edges() == 1
assert net.successors['a'] == set()
assert net.outgoing['a'] == set()
assert net.incident_edges['a'] == {f}
net.remove_edge('f')
assert net.number_of_edges() == 0
assert net.incident_edges['a'] == set()
a = Node('a')
b = Node('b')
e = Edge(a, b, uid='e')
f = Edge(a, b, uid='f')
g = Edge(a, b, uid='g')
net = Network(multiedges=True)
net.add_edges(e, f, g)
assert net.number_of_edges() == 3
assert e and f and g in net.edges['a', 'b']
net.remove_edge('a', 'b', uid='g')
assert net.number_of_edges() == 2
assert g not in net.edges['a', 'b']
net.remove_edge('a', 'b')
assert net.number_of_edges() == 0
assert len(net.edges['a', 'b']) == 0
def test_network_properties():
"""Test network properties."""
net = Network()
net.add_edge('a', 'b', uid='a-b')
net.add_edge('b', 'c', uid='b-c')
net.add_edge('c', 'a', uid='c-a')
assert net.successors['c'] == {net.nodes['a']}
assert net.incoming['a'] == {net.edges['c-a']}
net.remove_edge('c-a')
assert net.successors['c'] == set()
assert net.incoming['a'] == set()