diff --git a/tests/test_nav_theme.py b/tests/test_nav_theme.py
new file mode 100644
index 0000000..1c4c29e
--- /dev/null
+++ b/tests/test_nav_theme.py
@@ -0,0 +1,37 @@
+"""Navigation (#51) et bascule Dark/Light (#52).
+
+L'accordéon de la barre latérale omettait la section admin :
+le JS posait nav-closed-admin, mais aucun style ne la suivait.
+Le thème clair, lui, doit être atteignable par un bouton et
+mémorisé, avec les jetons draco clairs.
+"""
+
+
+def test_admin_accordion_closes(client, fake_gitea):
+    css = client.get("/static/css/style.css").text
+    assert 'body.nav-closed-admin [data-group="admin"] .side-acc' in css
+    assert 'body.nav-closed-admin [data-group="admin"] .side-chevron' in css
+
+
+def test_theme_toggle_present_and_versioned(client, fake_gitea):
+    page = client.get("/")
+    assert 'id="theme-toggle"' in page.text
+    assert "Mode clair" in page.text
+    assert "/static/js/nav.js?v=" in page.text
+
+
+def test_theme_js_contract(client, fake_gitea):
+    js = client.get("/static/js/nav.js").text
+    assert "kanbante-theme" in js
+    assert "theme-toggle" in js
+    assert "data-theme" in js
+
+
+def test_light_theme_tokens(client, fake_gitea):
+    css = client.get("/static/css/style.css").text
+    assert 'html[data-theme="light"]' in css
+    assert "--bg: #f2f2f0;" in css
+    assert "--surface: #ffffff;" in css
+    assert "--accent-2: #a92e63;" in css
+    assert 'html[data-theme="light"] .draco-bar' in css
+    assert 'html[data-theme="light"] .card-menu' in css