def test_repr_str_and_label(self) -> None:
mg = MultiGraph([(2, 1), (1, 2)])
assert mg.get_edge(
2, 1).label == "(1, 2)", "multiedge label should be (1, 2)"
assert (mg.get_edge(2, 1).__str__() == mg.get_edge(
2, 1).__repr__()), "edge __repr__ should equal __str__"
assert (mg.get_edge(2, 1).__str__() == "(1, 2), (1, 2)"
), "edge __str__ should be '(1, 2), (1, 2)'"
mg.add_edge(3, 4, weight=1.5)
assert mg.get_edge(
2, 1).label == "(1, 2)", "multiedge label should be (1, 2)"
assert (
mg.get_edge(2, 1).__str__() == "(1, 2, 1.0), (1, 2, 1.0)"
), "edge __str__ should be '(1, 2, 1.0), (1, 2, 1.0)' after adding weighted edge to graph"
def test_issubclass_and_isinstance(self) -> None:
g = MultiGraph()
edge: MultiEdge = g.add_edge(1, 2)
assert isinstance(
edge, edge_module.MultiEdgeBase
), "edge should be an instance of superclass MultiEdgeBase"
assert isinstance(edge,
MultiEdge), "edge should be an MultiEdge instance"
assert issubclass(MultiEdge, edge_module.MultiEdgeBase
), "MultiEdge should be MultiEdgeBase subclass"
def test_degree(self) -> None:
g = MultiGraph()
v0 = g.add_vertex(0)
assert v0.degree == 0, "vertex 0 should have degree 0"
g.add_edge(1, 1)
assert g[1].degree == 2, "vertex with self loop should have degree 2"
g.add_edge(1, 1)
assert g[
1].degree == 4, "vertex with two parallel self loops should have degree 4"
g.add_edge(2, 3)
assert g[2].degree == 1, "vertex 2 should have degree 1"
g.add_edge(2, 3)
assert g[
2].degree == 2, "vertex 2 with two parallel edge connections should have degree 2"