Add tests

+from webint_system import app
+
+
+def test_index():
+    response = app.get("")
+    assert response.status == "200 OK"
+
+    def get_headings(h):
+        return [_.text for _ in response.dom.select(f"h{h}")]
+
+    assert get_headings(1) == ["System"]
+    assert get_headings(2) == ["Addresses", "Software", "Settings"]
+    assert get_headings(3) == ["Clearnet", "Darknet", "Routes", "Wrappers"]