tests: test routing of index

For sake of completeness test the presence of '/' and '/index.html' as
well.

Signed-off-by: Johannes Thumshirn <jth@kernel.org>

tests/test_index.py

@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-3.0
+import os
+
+def test_index_html(app, client):
+    res = client.get('/index.html')
+    assert res.status_code == 200
+
+
+def test_index_slash(app, client):
+    res = client.get('/')
+    assert res.status_code == 200