Add exception note grouping test

tests/test_validation.py

@@ -244,3 +244,20 @@ class Test:
 
     assert match.cl == exc.value.cl
     assert rest.cl == exc.value.cl
+
+
+def test_note_grouping():
+    """Our ExceptionGroups can group their subexceptions by notes."""
+    exc1 = ValueError()
+    exc2 = KeyError()
+    exc3 = TypeError()
+
+    exc2.add_note(note := IterableValidationNote("Test Note", 0, int))
+    exc3.add_note("A string note")
+
+    exc = IterableValidationError("Test", [exc1, exc2, exc3], list[int])
+
+    with_notes, without_notes = exc.group_exceptions()
+
+    assert with_notes == [(exc2, note)]
+    assert without_notes == [exc1, exc3]