Improve test coverage expanders stochastic graph generators (#6073)

* Update test_stochastic.py

* Add comment describing test.

Co-authored-by: Ross Barnowski <rossbar@berkeley.edu>

1 files changed, 11 insertions, 0 deletions

diff --git a/networkx/generators/tests/test_stochastic.py b/networkx/generators/tests/test_stochastic.py
index d75a6a05..3f48f0d6 100644
--- a/networkx/generators/tests/test_stochastic.py
+++ b/networkx/generators/tests/test_stochastic.py
@@ -51,6 +51,17 @@ class TestStochasticGraph:
             (0, 2, d),
         ]
 
+    def test_zero_weights(self):
+        """Smoke test: ensure ZeroDivisionError is not raised."""
+        G = nx.DiGraph()
+        G.add_edge(0, 1, weight=0)
+        G.add_edge(0, 2, weight=0)
+        S = nx.stochastic_graph(G)
+        assert sorted(S.edges(data=True)) == [
+            (0, 1, {"weight": 0}),
+            (0, 2, {"weight": 0}),
+        ]
+
     def test_graph_disallowed(self):
         with pytest.raises(nx.NetworkXNotImplemented):
             nx.stochastic_graph(nx.Graph())