diff --git a/slhx-js/tests/runtime.rs b/slhx-js/tests/runtime.rs
index 3f44fff..c0b1d15 100644
--- a/slhx-js/tests/runtime.rs
+++ b/slhx-js/tests/runtime.rs
@@ -9,6 +9,17 @@ fn runtime_posts_urlencoded_forms_by_default() {
     assert!(source.contains("application/x-www-form-urlencoded;charset=UTF-8"));
 }
 
+#[test]
+fn runtime_interval_dispatch_avoids_duplicate_timers() {
+    // req: convention/005
+    let source = slhx_js::RUNTIME_JS;
+
+    assert!(source.contains("root.querySelectorAll(\"[data-slhx-every]\")"));
+    assert!(source.contains("if (timers.has(el)) return"));
+    assert!(source.contains("setInterval(() => document.contains(el) ? send(el, \"every\")"));
+    assert!(source.contains("clearInterval(timers.get(el))"));
+}
+
 #[test]
 fn runtime_toggles_pending_conventions_around_requests() {
     // req: convention/007 req: convention/008