diff --git a/optuna_dashboard/streamlit/_streamlit_helper.py b/optuna_dashboard/streamlit/_streamlit_helper.py
index 719b5c0a..814a6327 100644
--- a/optuna_dashboard/streamlit/_streamlit_helper.py
+++ b/optuna_dashboard/streamlit/_streamlit_helper.py
@@ -66,7 +66,7 @@ def _render_widgets(
                 )
             elif widget["type"] == "text":
                 # NOTE: Current implementation ignores "optional".
-                value = st.text_input(_format_description(widget["description"]))
+                value = st.text_input(_format_description(widget["description"]))  # type: ignore
             elif widget["type"] == "user_attr":
                 value = trial.user_attrs[widget["key"]]
             else:
diff --git a/python_tests/streamlit/__init__.py b/python_tests/streamlit/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/python_tests/streamlit/test_streamlit_helper.py b/python_tests/streamlit/test_streamlit_helper.py
new file mode 100644
index 00000000..3bd903d8
--- /dev/null
+++ b/python_tests/streamlit/test_streamlit_helper.py
@@ -0,0 +1,98 @@
+import itertools
+from typing import Sequence
+
+import optuna
+from optuna_dashboard import ChoiceWidget
+from optuna_dashboard import register_objective_form_widgets
+from optuna_dashboard import register_user_attr_form_widgets
+from optuna_dashboard import save_note
+from optuna_dashboard import SliderWidget
+from optuna_dashboard import TextInputWidget
+from optuna_dashboard.streamlit import render_objective_form_widgets
+from optuna_dashboard.streamlit import render_trial_note
+from optuna_dashboard.streamlit import render_user_attr_form_widgets
+import pytest
+
+
+@pytest.mark.parametrize("note", ["test", ""])
+def test_render_trial_note(note: str) -> None:
+    study = optuna.create_study()
+
+    trial = study.ask()
+    save_note(trial, note)
+
+    render_trial_note(study, study.trials[0])
+
+
+def test_render_trial_note_without_note() -> None:
+    study = optuna.create_study()
+
+    study.ask()
+
+    render_trial_note(study, study.trials[0])
+
+
+widget_list_for_user_attr = [
+    ChoiceWidget(
+        choices=["Good", "Bad"],
+        values=[1, -1],
+        description="description",
+        user_attr_key="choice",
+    ),
+    SliderWidget(
+        min=1,
+        max=5,
+        step=1,
+        labels=[(1, "Bad"), (5, "Good")],
+        description="description",
+        user_attr_key="slider",
+    ),
+    TextInputWidget(description="description", user_attr_key="text1"),
+    TextInputWidget(description="description", user_attr_key="text2"),
+]
+
+widgets_combinations_for_user_attr = []
+# Test widget combinations.
+for r in range(len(widget_list_for_user_attr) + 1):
+    widgets_combinations_for_user_attr += list(
+        itertools.combinations(widget_list_for_user_attr, r)
+    )
+
+
+@pytest.mark.parametrize("widgets", widgets_combinations_for_user_attr)
+def test_render_user_attr_form_widgets(
+    widgets: Sequence[ChoiceWidget | SliderWidget | TextInputWidget],
+) -> None:
+    study = optuna.create_study()
+    register_user_attr_form_widgets(study, widgets)  # type: ignore
+
+    study.ask()
+    render_user_attr_form_widgets(study, study.trials[0])
+
+
+widget_list_for_objective = [
+    ChoiceWidget(
+        choices=["Good", "Bad"],
+        values=[1, -1],
+        description="description",
+    ),
+    SliderWidget(
+        min=1,
+        max=5,
+        step=1,
+        labels=[(1, "Bad"), (5, "Good")],
+        description="description",
+    ),
+    TextInputWidget(description="description"),
+]
+
+
+@pytest.mark.parametrize("widget", widget_list_for_objective)
+def test_render_objective_form_widgets(
+    widget: ChoiceWidget | SliderWidget | TextInputWidget,
+) -> None:
+    study = optuna.create_study()
+    register_objective_form_widgets(study, [widget])  # type: ignore
+
+    study.ask()
+    render_objective_form_widgets(study, study.trials[0])