diff --git a/lib/aprsme/cache.ex b/lib/aprsme/cache.ex
index 5489d18..48556d8 100644
--- a/lib/aprsme/cache.ex
+++ b/lib/aprsme/cache.ex
@@ -172,11 +172,9 @@ defmodule Aprsme.Cache do
   @impl true
   def handle_call({:stats, cache_name}, _from, state) do
     result =
-      try do
-        info = :ets.info(cache_name)
-        {:ok, %{size: Keyword.get(info, :size, 0)}}
-      rescue
-        ArgumentError -> {:error, :no_cache}
+      case :ets.info(cache_name) do
+        :undefined -> {:error, :no_cache}
+        info when is_list(info) -> {:ok, %{size: Keyword.get(info, :size, 0)}}
       end
 
     {:reply, result, state}
diff --git a/test/aprsme/cache_test.exs b/test/aprsme/cache_test.exs
index b753ee9..b1af4c6 100644
--- a/test/aprsme/cache_test.exs
+++ b/test/aprsme/cache_test.exs
@@ -138,5 +138,52 @@ defmodule Aprsme.CacheTest do
     test "put returns error for non-existent table" do
       assert {:error, :no_cache} = Cache.put(:nonexistent_table, :key, "value")
     end
+
+    test "del returns error for non-existent table" do
+      assert {:error, :no_cache} = Cache.del(:nonexistent_table, :key)
+    end
+
+    test "clear returns error for non-existent table" do
+      assert {:error, :no_cache} = Cache.clear(:nonexistent_table)
+    end
+  end
+
+  describe "stats/1" do
+    test "returns the current size of the cache" do
+      Cache.put(@table_name, :a, 1)
+      Cache.put(@table_name, :b, 2)
+      assert {:ok, %{size: size}} = Cache.stats(@table_name)
+      assert size == 2
+    end
+
+    test "returns error for non-existent tables" do
+      assert {:error, :no_cache} = Cache.stats(:does_not_exist_table)
+    end
+  end
+
+  describe "legacy 2-element tuple lookups" do
+    test "get handles tuples that lack an expires_at" do
+      :ets.insert(@table_name, {:legacy_key, "legacy_value"})
+      assert {:ok, "legacy_value"} = Cache.get(@table_name, :legacy_key)
+    end
+
+    test "ttl handles legacy tuples (returns nil)" do
+      :ets.insert(@table_name, {:legacy_key, "legacy_value"})
+      assert {:ok, nil} = Cache.ttl(@table_name, :legacy_key)
+    end
+  end
+
+  describe "to_timeout/1 with more units" do
+    test "supports :millisecond/:milliseconds keys" do
+      assert Cache.to_timeout(millisecond: 500) == 500
+      assert Cache.to_timeout(milliseconds: 250) == 250
+    end
+
+    test "ignores invalid TTL values in put/4" do
+      # Negative TTL → :infinity under the clause that matches `_ -> :infinity`.
+      assert {:ok, true} = Cache.put(@table_name, :inf_key, "val", ttl: -1)
+      assert {:ok, "val"} = Cache.get(@table_name, :inf_key)
+      assert {:ok, nil} = Cache.ttl(@table_name, :inf_key)
+    end
   end
 end