test: DatabaseMetrics pool-not-registered path

test/aprsme/telemetry/database_metrics_test.exs

@@ -57,6 +57,34 @@ defmodule Aprsme.Telemetry.DatabaseMetricsTest do
     end
   end
 
+  describe "collect_db_pool_metrics/0 when Repo is not running" do
+    test "emits unavailable metrics when no Repo is registered" do
+      # Stop the Repo for this test — we need to restart it afterward to avoid
+      # breaking downstream tests.
+      repo_pid = Process.whereis(Aprsme.Repo)
+
+      if repo_pid do
+        # Temporarily unregister without stopping to avoid disrupting other tests.
+        :erlang.unregister(Aprsme.Repo)
+
+        on_exit(fn ->
+          if !Process.whereis(Aprsme.Repo) do
+            true = Process.register(repo_pid, Aprsme.Repo)
+          end
+        end)
+      end
+
+      attach_collector([:aprsme, :repo, :pool])
+      DatabaseMetrics.collect_db_pool_metrics()
+
+      assert_receive {:telemetry, [:aprsme, :repo, :pool], measurements, _}, 1_000
+      # The "unavailable" helper reports mostly zeros.
+      assert measurements.size == Application.get_env(:aprsme, Aprsme.Repo)[:pool_size] || 10
+      assert measurements.idle == 0
+      assert measurements.busy == 0
+    end
+  end
+
   describe "collect_postgres_metrics/0 outside :test env" do
     test "emits database, connections, packets_table and query_stats telemetry events" do
       original = Application.get_env(:aprsme, :env)