diff --git a/tests/test_tableau_hscroll.py b/tests/test_tableau_hscroll.py
new file mode 100644
index 0000000..6699c89
--- /dev/null
+++ b/tests/test_tableau_hscroll.py
@@ -0,0 +1,16 @@
+from dash.testing.composite import DashComposite
+
+
+def test_tableau_hscroll_bar_present(dash_duo: DashComposite):
+    """La barre miroir est injectée et l'en-tête est collant sur /tableau."""
+    from src.app import app
+
+    dash_duo.start_server(app)
+    dash_duo.wait_for_page(f"{dash_duo.server_url}/tableau")
+    dash_duo.wait_for_element(".marches_table", timeout=20)
+    # Barre miroir injectée par table_hscroll.js
+    dash_duo.wait_for_element(".marches_table .dt-hscroll", timeout=10)
+
+    header = dash_duo.find_element(".marches_table th.dash-header")
+    position = header.value_of_css_property("position")
+    assert position == "sticky"