adding test

changedetectionio/tests/proxy_list/test_select_custom_proxy.py

@@ -49,3 +49,22 @@ def test_select_custom(client, live_server, measure_memory_usage):
     #
     # Now we should see the request in the container logs for "squid-squid-custom" because it will be the only default
 
+
+def test_custom_proxy_validation(client, live_server, measure_memory_usage):
+    #  live_server_setup(live_server) # Setup on conftest per function
+
+    # Goto settings, add our custom one
+    res = client.post(
+        url_for("settings.settings_page"),
+        data={
+            "requests-time_between_check-minutes": 180,
+            "application-ignore_whitespace": "y",
+            "application-fetch_backend": 'html_requests',
+            "requests-extra_proxies-0-proxy_name": "custom-test-proxy",
+            "requests-extra_proxies-0-proxy_url": "xxxxhtt/333??p://test:awesome@squid-custom:3128",
+        },
+        follow_redirects=True
+    )
+
+    assert b"Settings updated." not in res.data
+    assert b'Proxy URLs must start with' in res.data