Fixed database typo and removed unnecessary class identifier.

venv/Lib/site-packages/networkx/utils/tests/test_unionfind.py

@@ -0,0 +1,42 @@
+import networkx as nx
+
+
+def test_unionfind():
+    # Fixed by: 2cddd5958689bdecdcd89b91ac9aaf6ce0e4f6b8
+    # Previously (in 2.x), the UnionFind class could handle mixed types.
+    # But in Python 3.x, this causes a TypeError such as:
+    #   TypeError: unorderable types: str() > int()
+    #
+    # Now we just make sure that no exception is raised.
+    x = nx.utils.UnionFind()
+    x.union(0, "a")
+
+
+def test_subtree_union():
+    # See https://github.com/networkx/networkx/pull/3224
+    # (35db1b551ee65780794a357794f521d8768d5049).
+    # Test if subtree unions hare handled correctly by to_sets().
+    uf = nx.utils.UnionFind()
+    uf.union(1, 2)
+    uf.union(3, 4)
+    uf.union(4, 5)
+    uf.union(1, 5)
+    assert list(uf.to_sets()) == [{1, 2, 3, 4, 5}]
+
+
+def test_unionfind_weights():
+    # Tests if weights are computed correctly with unions of many elements
+    uf = nx.utils.UnionFind()
+    uf.union(1, 4, 7)
+    uf.union(2, 5, 8)
+    uf.union(3, 6, 9)
+    uf.union(1, 2, 3, 4, 5, 6, 7, 8, 9)
+    assert uf.weights[uf[1]] == 9
+
+
+def test_empty_union():
+    # Tests if a null-union does nothing.
+    uf = nx.utils.UnionFind((0, 1))
+    uf.union()
+    assert uf[0] == 0
+    assert uf[1] == 1