Implement JSON API for note

python_tests/test_note.py

@@ -0,0 +1,19 @@
+from unittest import TestCase
+from unittest.mock import patch
+
+from optuna_dashboard import _note as note
+
+
+class NoteTestCase(TestCase):
+    @patch("optuna_dashboard._note.SYSTEM_ATTR_MAX_LENGTH", 5)
+    def test_split_and_concat_note_body(self) -> None:
+        for dummy_body_str, attr_len in [
+            ("012", 1),
+            ("01234", 1),
+            ("012345", 2),
+        ]:
+            with self.subTest(f"with_{dummy_body_str}_{attr_len}"):
+                attrs = note.split_body(dummy_body_str)
+                assert len(attrs) == attr_len
+                actual = note.concat_body(attrs)
+                assert dummy_body_str == actual