def test_adjacent():
g = Graph()
g.add_edge('a', 'b')
g.add_edge('a', 'c')
try:
g.adjacent('a', 'e')
except IndexError:
assert True
else:
assert False
assert g.adjacent('a', 'b') is True
assert g.adjacent('c', 'b') is False
def test_weighted_edges():
g = Graph()
g.add_edge('a', 'b')
g.add_edge('a', 'd')
g.add_edge('a', 'g')
g.add_edge('b', 'e')
g.add_edge('e', 'g')
g.add_edge('b', 'f')
g.add_edge('f', 'd')
g.add_edge('f', 'c')
g.add_edge('c', 'h')
assert g.adjacent('a', 'b') is True
assert g.adjacent('a', 'c') is False
g.del_edge('a', 'b')
assert g.neighbors('a') == ['d', 'g']