diff --git a/test/aprsme/is_test.exs b/test/aprsme/is_test.exs
index 338ed51..a1d53ba 100644
--- a/test/aprsme/is_test.exs
+++ b/test/aprsme/is_test.exs
@@ -498,6 +498,21 @@ defmodule Aprsme.IsTest do
     end
   end
 
+  describe "send_message/3 and /1 helpers" do
+    test "three-arg send_message delegates to send_message/1 without server running" do
+      # GenServer not running → send_message/1 returns {:error, :not_connected}.
+      assert {:error, :not_connected} = Aprsme.Is.send_message("FROM", "TO", "hi")
+    end
+
+    test "set_filter/1 without server running returns not_connected" do
+      assert {:error, :not_connected} = Aprsme.Is.set_filter("r/0/0/1")
+    end
+
+    test "list_active_filters/0 without server running returns not_connected" do
+      assert {:error, :not_connected} = Aprsme.Is.list_active_filters()
+    end
+  end
+
   describe "backpressure handling" do
     test "activate with nil socket is a no-op" do
       state = build_state(%{socket: nil, backpressure_active: false})