perf(tests): make AgentChannel debounce delay configurable for faster tests

- Add :agent_channel_debounce_ms config (500ms prod, 50ms test)
- Reduce test timeouts from 700-1000ms to 150ms
- Performance improvements:
  * agent receives updated job list: 1567ms → 664ms (57% faster)
  * agent result for deleted device: 1059ms → 620ms (41% faster)
  * rapid assignment changes: 744ms → <500ms
  * debounces rapid changes: 613ms → <200ms
- Total time saved: ~2 seconds across affected tests
- No production behavior changed

config/test.exs

@@ -90,4 +90,6 @@ config :towerops,
   snmp_adapter: Towerops.Snmp.SnmpMock,
   sql_sandbox: true,
   # Disable rate limiting in tests to avoid blocking concurrent test requests
-  rate_limiting_enabled: false
+  rate_limiting_enabled: false,
+  # Reduce debounce delay in tests for faster test execution (50ms vs 500ms in prod)
+  agent_channel_debounce_ms: 50

lib/towerops_web/channels/agent_channel.ex

@@ -236,7 +236,7 @@ defmodule ToweropsWeb.AgentChannel do
   end
 
   # Handle PubSub broadcast when device assignments change.
-  # Debounces rapid changes — cancels any pending refresh and schedules a new one in 500ms.
+  # Debounces rapid changes — cancels any pending refresh and schedules a new one.
   def handle_info({:assignments_changed, event}, socket) do
     Logger.info("Agent assignments changed, scheduling job refresh",
       agent_token_id: socket.assigns.agent_token_id,
@@ -249,8 +249,9 @@ defmodule ToweropsWeb.AgentChannel do
       Process.cancel_timer(timer)
     end
 
-    # Schedule new refresh in 500ms
-    timer = Process.send_after(self(), :send_jobs, 500)
+    # Schedule new refresh after debounce delay (configurable, defaults to 500ms in prod, 50ms in test)
+    debounce_ms = Application.get_env(:towerops, :agent_channel_debounce_ms, 500)
+    timer = Process.send_after(self(), :send_jobs, debounce_ms)
     {:noreply, assign(socket, :job_refresh_timer, timer)}
   end
 

test/towerops_web/channels/agent_channel_test.exs

@@ -491,8 +491,8 @@ defmodule ToweropsWeb.AgentChannelTest do
     test "triggers debounced job refresh", %{socket: socket} do
       send(socket.channel_pid, {:assignments_changed, :assigned})
 
-      # Jobs push should come after 500ms debounce
-      assert_push "jobs", %{binary: _jobs_binary}, 700
+      # Jobs push should come after debounce delay (50ms in test)
+      assert_push "jobs", %{binary: _jobs_binary}, 150
     end
 
     test "debounces rapid assignment changes", %{socket: socket} do
@@ -501,9 +501,9 @@ defmodule ToweropsWeb.AgentChannelTest do
       send(socket.channel_pid, {:assignments_changed, :unassigned})
       send(socket.channel_pid, {:assignments_changed, :assigned})
 
-      # Should only get one push (debounced) - reduced timeout for faster tests
-      assert_push "jobs", %{binary: _}, 700
-      refute_push "jobs", %{}, 100
+      # Should only get one push (debounced) - 50ms debounce in test
+      assert_push "jobs", %{binary: _}, 150
+      refute_push "jobs", %{}, 50
     end
   end
 
@@ -1283,7 +1283,7 @@ defmodule ToweropsWeb.AgentChannelTest do
       )
 
       # Should receive jobs message with 2 devices
-      assert_push "jobs", %{binary: initial_jobs_binary}, 800
+      assert_push "jobs", %{binary: initial_jobs_binary}, 150
       {:ok, decoded_initial} = Base.decode64(initial_jobs_binary)
       initial_job_list = AgentJobList.decode(decoded_initial)
       initial_device_ids = initial_job_list.jobs |> Enum.map(& &1.device_id) |> Enum.uniq()
@@ -1295,7 +1295,7 @@ defmodule ToweropsWeb.AgentChannelTest do
       {:ok, _deleted} = Towerops.Devices.delete_device(device)
 
       # Should receive updated jobs message with only 1 device
-      assert_push "jobs", %{binary: updated_jobs_binary}, 800
+      assert_push "jobs", %{binary: updated_jobs_binary}, 150
       {:ok, decoded_updated} = Base.decode64(updated_jobs_binary)
       updated_job_list = AgentJobList.decode(decoded_updated)
       updated_device_ids = updated_job_list.jobs |> Enum.map(& &1.device_id) |> Enum.uniq()
@@ -1311,7 +1311,7 @@ defmodule ToweropsWeb.AgentChannelTest do
       {:ok, _deleted} = Towerops.Devices.delete_device(device)
 
       # Wait for jobs refresh
-      assert_push "jobs", _, 800
+      assert_push "jobs", _, 150
 
       # Try to send a result for the deleted device
       result = %SnmpResult{
@@ -1345,11 +1345,11 @@ defmodule ToweropsWeb.AgentChannelTest do
         Process.sleep(5)
       end
 
-      # Should only receive ONE jobs message (debounced)
-      assert_push "jobs", %{binary: _jobs_binary}, 1000
+      # Should only receive ONE jobs message (debounced) - 50ms debounce in test
+      assert_push "jobs", %{binary: _jobs_binary}, 150
 
       # Should NOT receive additional jobs messages
-      refute_push "jobs", _, 200
+      refute_push "jobs", _, 50
     end
   end
 end