test(deterministic): add WL blank-node and no-bnode edge case tests

Signed-off-by: jdsika <carlo.van-driesten@bmw.de>

Author: jdsika

tests/linkml/test_generators/test_deterministic_output.py

@@ -260,6 +260,67 @@ def test_non_deterministic_is_default():
     assert gen.deterministic is False
 
 
+def test_wl_handles_structurally_similar_bnodes():
+    """Blank nodes with identical local structure but different named neighbours
+    must receive different WL signatures and thus different stable labels.
+
+    This tests the core WL property: two BNodes that differ only in their
+    connected named nodes (URIs/literals) must be distinguishable.
+    """
+    from rdflib import BNode, Graph, Literal, Namespace, URIRef
+
+    from linkml.utils.generator import deterministic_turtle
+
+    EX = Namespace("http://example.org/")
+    g = Graph()
+
+    # Two restrictions with same structure but different property URIs
+    r1 = BNode()
+    g.add((r1, URIRef("http://www.w3.org/1999/02/22-rdf-syntax-ns#type"),
+           URIRef("http://www.w3.org/2002/07/owl#Restriction")))
+    g.add((r1, URIRef("http://www.w3.org/2002/07/owl#onProperty"), EX.alpha))
+    g.add((r1, URIRef("http://www.w3.org/2002/07/owl#allValuesFrom"), EX.Target1))
+
+    r2 = BNode()
+    g.add((r2, URIRef("http://www.w3.org/1999/02/22-rdf-syntax-ns#type"),
+           URIRef("http://www.w3.org/2002/07/owl#Restriction")))
+    g.add((r2, URIRef("http://www.w3.org/2002/07/owl#onProperty"), EX.beta))
+    g.add((r2, URIRef("http://www.w3.org/2002/07/owl#allValuesFrom"), EX.Target2))
+
+    g.add((EX.MyClass, URIRef("http://www.w3.org/2000/01/rdf-schema#subClassOf"), r1))
+    g.add((EX.MyClass, URIRef("http://www.w3.org/2000/01/rdf-schema#subClassOf"), r2))
+
+    # Must be deterministic across runs
+    out1 = deterministic_turtle(g)
+    out2 = deterministic_turtle(g)
+    assert out1 == out2, "WL-based serializer is not deterministic for similar BNodes"
+
+    # Both restrictions must appear (not collapsed)
+    assert "alpha" in out1
+    assert "beta" in out1
+
+
+def test_deterministic_turtle_no_bnodes():
+    """Graphs with no blank nodes should still produce sorted, deterministic output."""
+    from rdflib import Graph, Literal, Namespace, URIRef
+
+    from linkml.utils.generator import deterministic_turtle
+
+    EX = Namespace("http://example.org/")
+    g = Graph()
+    g.add((EX.B, URIRef("http://www.w3.org/2000/01/rdf-schema#label"), Literal("B")))
+    g.add((EX.A, URIRef("http://www.w3.org/2000/01/rdf-schema#label"), Literal("A")))
+
+    out1 = deterministic_turtle(g)
+    out2 = deterministic_turtle(g)
+    assert out1 == out2
+
+    # A should appear before B (sorted)
+    a_pos = out1.find("example.org/A")
+    b_pos = out1.find("example.org/B")
+    assert a_pos < b_pos, "Triples should be sorted: A before B"
+
+
 @pytest.mark.xfail(
     reason=(
         "Collection sorting (owl:oneOf, sh:in) in deterministic mode intentionally "