def test_get_edge_bad_input(self):
g = Graph()
assert g.get_edge(None, None) is None
assert g.get_edge(None, v) is None
assert g.get_edge(v, None) is None
assert g.get_edge(v, 'fs') is None
assert g.get_edge(v, 3) is None
def test_get_edge_false(self):
g = Graph()
assert None is g.get_edge(v, v)
assert None is g.get_edge(w, w)
assert None is g.get_edge(v, w)
assert None is g.get_edge(w, v)
g = Graph([v, w])
assert None is g.get_edge(v, v)
assert None is g.get_edge(w, w)
assert None is g.get_edge(v, w)
assert None is g.get_edge(w, v)
g = Graph([v, w, x], [vx, ])
assert None is g.get_edge(v, v)
assert None is g.get_edge(w, w)
assert None is g.get_edge(v, w)
assert None is g.get_edge(w, v)
def test_get_edge_true(self):
g = Graph([v, w], [vw, ])
assert vw == g.get_edge(v, w)
assert vw == g.get_edge(w, v)
