Added few tests for /generators/duplication.py and /generators/geomet… (

networkx#6976)

* Added few tests for /generators/duplication.py and /generators/geometric.py. Corrected an exception statement in geometric.py (r must be >=0 instead of r must be >= 1)

* Added kargs to make it more readable. And added few more tests.

* STY: Minor signature cleanup.

* Update test for r in range [0, 1].

* Add test for general edge scaling with increasing r.

---------

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

networkx/generators/geometric.py

@@ -686,7 +686,7 @@ def navigable_small_world_graph(n, p=1, q=1, r=2, dim=2, seed=None):
     if q < 0:
         raise nx.NetworkXException("q must be >= 0")
     if r < 0:
-        raise nx.NetworkXException("r must be >= 1")
+        raise nx.NetworkXException("r must be >= 0")
 
     G = nx.DiGraph()
     nodes = list(product(range(n), repeat=dim))

networkx/generators/tests/test_duplication.py

@@ -18,18 +18,29 @@ class TestDuplicationDivergenceGraph:
     """
 
     def test_final_size(self):
-        G = duplication_divergence_graph(3, 1)
+        G = duplication_divergence_graph(3, p=1)
         assert len(G) == 3
-        G = duplication_divergence_graph(3, 1, seed=42)
+        G = duplication_divergence_graph(3, p=1, seed=42)
         assert len(G) == 3
 
     def test_probability_too_large(self):
         with pytest.raises(NetworkXError):
-            duplication_divergence_graph(3, 2)
+            duplication_divergence_graph(3, p=2)
 
     def test_probability_too_small(self):
         with pytest.raises(NetworkXError):
-            duplication_divergence_graph(3, -1)
+            duplication_divergence_graph(3, p=-1)
+
+    def test_non_extreme_probability_value(self):
+        G = duplication_divergence_graph(6, p=0.3, seed=42)
+        assert len(G) == 6
+        assert list(G.degree()) == [(0, 2), (1, 3), (2, 2), (3, 3), (4, 1), (5, 1)]
+
+    def test_minimum_desired_nodes(self):
+        with pytest.raises(
+            NetworkXError, match=".*n must be greater than or equal to 2"
+        ):
+            duplication_divergence_graph(1, p=1)
 
 
 class TestPartialDuplicationGraph:

networkx/generators/tests/test_geometric.py

@@ -249,6 +249,39 @@ def test_navigable_small_world(self):
         gg = nx.grid_graph([5]).to_directed()
         assert nx.is_isomorphic(G, gg)
 
+    def test_invalid_diameter_value(self):
+        with pytest.raises(nx.NetworkXException, match=".*p must be >= 1"):
+            nx.navigable_small_world_graph(5, p=0, q=0, dim=1)
+
+    def test_invalid_long_range_connections_value(self):
+        with pytest.raises(nx.NetworkXException, match=".*q must be >= 0"):
+            nx.navigable_small_world_graph(5, p=1, q=-1, dim=1)
+
+    def test_invalid_exponent_for_decaying_probability_value(self):
+        with pytest.raises(nx.NetworkXException, match=".*r must be >= 0"):
+            nx.navigable_small_world_graph(5, p=1, q=0, r=-1, dim=1)
+
+    def test_r_between_0_and_1(self):
+        """Smoke test for radius in range [0, 1]"""
+        # q=0 means no long-range connections
+        G = nx.navigable_small_world_graph(3, p=1, q=0, r=0.5, dim=2, seed=42)
+        expected = nx.grid_2d_graph(3, 3, create_using=nx.DiGraph)
+        assert nx.utils.graphs_equal(G, expected)
+
+    @pytest.mark.parametrize("seed", range(2478, 2578, 10))
+    def test_r_general_scaling(self, seed):
+        """The probability of adding a long-range edge scales with `1 / dist**r`,
+        so a navigable_small_world graph created with r < 1 should generally
+        result in more edges than a navigable_small_world graph with r >= 1
+        (for 0 < q << n).
+
+        N.B. this is probabilistic, so this test may not hold for all seeds."""
+        G1 = nx.navigable_small_world_graph(7, q=3, r=0.5, seed=seed)
+        G2 = nx.navigable_small_world_graph(7, q=3, r=1, seed=seed)
+        G3 = nx.navigable_small_world_graph(7, q=3, r=2, seed=seed)
+        assert G1.number_of_edges() > G2.number_of_edges()
+        assert G2.number_of_edges() > G3.number_of_edges()
+
 
 class TestThresholdedRandomGeometricGraph:
     """Unit tests for :func:`~networkx.thresholded_random_geometric_graph`"""