def test_adjacent():
g = Graph()
g.add_edge(u"A", u"C")
g.add_node(u"B")
print g.edges()
assert g.adjacent(u"A", u"C") is True
assert g.adjacent(u"C", u"A") is True
assert g.adjacent(u"B", u"C") is False
assert g.adjacent(u"B", u"A") is False
with pytest.raises(KeyError):
g.adjacent(u"A", u"D")
def test_del_edge():
g = Graph()
g.add_edge(u"A", u"C")
g.del_edge(u"A", u"C")
assert (u"A", u"C") not in g.edges()
assert u"A" in g.nodes()
assert u"C" in g.nodes()
def test_edges_empty():
g = Graph()
assert g.edges() == []
def test_add_edge_two_new_nodes():
g = Graph()
g.add_edge(u"A", u"C")
assert u"A" in g.nodes()
assert u"C" in g.nodes()
assert (u"A", u"C") in g.edges()
def test_add_edge():
g = Graph()
g.add_node(u"A")
g.add_node(u"B")
g.add_edge(u"A", u"B")
assert (u"A", u"B") in g.edges()
