Validate axis-label manifold names

src/pyrecest/evaluation/get_axis_label.py

@@ -1,5 +1,11 @@
+def _normalize_manifold_name(manifold_name):
+    if not isinstance(manifold_name, str) or not manifold_name.strip():
+        raise ValueError("manifold_name must be a non-empty string")
+    return manifold_name.strip().lower()
+
+
 def get_axis_label(manifold_name):
-    normalized_name = manifold_name.lower()
+    normalized_name = _normalize_manifold_name(manifold_name)
 
     if "circlesymm" in normalized_name:
         error_label = "Error in radian"

tests/test_axis_labels.py

@@ -26,3 +26,13 @@ def test_specific_manifolds_are_not_shadowed_by_generic_substrings(
 )
 def test_generic_manifold_axis_labels_are_preserved(manifold_name, expected_label):
     assert get_axis_label(manifold_name) == expected_label
+
+
+@pytest.mark.parametrize("manifold_name", [None, "", "   "])
+def test_axis_label_rejects_invalid_manifold_names(manifold_name):
+    with pytest.raises(ValueError, match="manifold_name must be a non-empty string"):
+        get_axis_label(manifold_name)
+
+
+def test_axis_label_strips_manifold_name_whitespace():
+    assert get_axis_label("  hypersphere  ") == "Error (orthodromic distance) in radian"