test: Add test for Graph.items (RDFLib#2819)

Co-authored-by: Ashley Sommer <[email protected]>

Author: progval

test/test_graph/test_graph_items.py

@@ -1,4 +1,40 @@
-from rdflib import RDF, Graph
+from rdflib import RDF, Graph, Namespace
+
+EX = Namespace("http://example.org/")
+
+
+def test_items():
+    g = Graph().parse(
+        data="""
+        @prefix : <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
+
+        <> :value (
+            <http://example.org/thing1>
+            <http://example.org/thing2>
+        ).
+
+        <> :value (
+            <http://example.org/thing3>
+        ).
+
+        <> :value ().
+
+        <> :value (
+            <http://example.org/thing4>
+            <http://example.org/thing5>
+            <http://example.org/thing6>
+        ).
+        """,
+        format="turtle",
+    )
+
+    values = {tuple(g.items(v)) for v in g.objects(None, RDF.value)}
+    assert values == {
+        (EX.thing1, EX.thing2),
+        (EX.thing3,),
+        (),
+        (EX.thing4, EX.thing5, EX.thing6),
+    }
 
 
 def test_recursive_list_detection():