diff --git a/test/aprs/packet_replay_test.exs b/test/aprs/packet_replay_test.exs
new file mode 100644
index 0000000..3311852
--- /dev/null
+++ b/test/aprs/packet_replay_test.exs
@@ -0,0 +1,725 @@
+defmodule Aprs.PacketReplayTest do
+  use Aprs.DataCase, async: true
+
+  import Mox
+
+  alias Aprs.PacketReplay
+  alias AprsWeb.Endpoint
+  alias Phoenix.Socket.Broadcast
+
+  setup :verify_on_exit!
+
+  setup do
+    # Mock the Packets module functions
+    Mox.defmock(MockPackets, for: Aprs.PacketsBehaviour)
+    Application.put_env(:aprs, :packets_module, MockPackets)
+
+    # Start a test registry for the packet replay processes
+    start_supervised!({Registry, keys: :unique, name: Aprs.ReplayRegistry})
+
+    # Example test data
+    user_id = "test_user_#{:rand.uniform(10_000)}"
+    # New York area
+    bounds = [-74.0, 40.0, -73.0, 41.0]
+
+    mock_packet = %{
+      id: "test_packet_1",
+      received_at: DateTime.utc_now(),
+      lat: 40.5,
+      lon: -73.5,
+      sender: "N0CALL",
+      data_type: "position"
+    }
+
+    %{
+      user_id: user_id,
+      bounds: bounds,
+      mock_packet: mock_packet
+    }
+  end
+
+  describe "start_replay/1" do
+    test "starts replay with required options", %{user_id: user_id, bounds: bounds} do
+      opts = [user_id: user_id, bounds: bounds]
+
+      assert {:ok, pid} = PacketReplay.start_replay(opts)
+      assert is_pid(pid)
+      assert Process.alive?(pid)
+
+      # Clean up
+      GenServer.stop(pid)
+    end
+
+    test "raises error when bounds are missing", %{user_id: user_id} do
+      opts = [user_id: user_id]
+
+      assert_raise ArgumentError, "Map bounds are required for packet replay", fn ->
+        PacketReplay.start_replay(opts)
+      end
+    end
+
+    test "starts replay with all optional parameters", %{user_id: user_id, bounds: bounds} do
+      opts = [
+        user_id: user_id,
+        bounds: bounds,
+        callsign: "N0CALL",
+        start_time: DateTime.add(DateTime.utc_now(), -3600, :second),
+        end_time: DateTime.utc_now(),
+        replay_speed: 2.0,
+        limit: 1000,
+        with_position: true
+      ]
+
+      assert {:ok, pid} = PacketReplay.start_replay(opts)
+      assert Process.alive?(pid)
+
+      # Clean up
+      GenServer.stop(pid)
+    end
+
+    test "fails when user_id is missing", %{bounds: bounds} do
+      opts = [bounds: bounds]
+
+      assert_raise KeyError, fn ->
+        PacketReplay.start_replay(opts)
+      end
+    end
+
+    test "registers process with unique name per user", %{bounds: bounds} do
+      user_id1 = "user1"
+      user_id2 = "user2"
+
+      {:ok, pid1} = PacketReplay.start_replay(user_id: user_id1, bounds: bounds)
+      {:ok, pid2} = PacketReplay.start_replay(user_id: user_id2, bounds: bounds)
+
+      assert pid1 != pid2
+      assert Process.alive?(pid1)
+      assert Process.alive?(pid2)
+
+      # Clean up
+      GenServer.stop(pid1)
+      GenServer.stop(pid2)
+    end
+  end
+
+  describe "stop_replay/1" do
+    test "stops an active replay session", %{user_id: user_id, bounds: bounds} do
+      {:ok, pid} = PacketReplay.start_replay(user_id: user_id, bounds: bounds)
+      assert Process.alive?(pid)
+
+      assert :ok = PacketReplay.stop_replay(user_id)
+
+      # Give it a moment to stop
+      Process.sleep(10)
+      refute Process.alive?(pid)
+    end
+
+    test "returns error when no replay session exists" do
+      assert {:error, :not_found} = PacketReplay.stop_replay("nonexistent_user")
+    end
+  end
+
+  describe "pause_replay/1" do
+    test "pauses an active replay session", %{user_id: user_id, bounds: bounds} do
+      {:ok, _pid} = PacketReplay.start_replay(user_id: user_id, bounds: bounds)
+
+      assert :ok = PacketReplay.pause_replay(user_id)
+
+      # Verify state
+      info = PacketReplay.get_replay_info(user_id)
+      assert info.paused == true
+
+      # Clean up
+      PacketReplay.stop_replay(user_id)
+    end
+
+    test "fails when replay session doesn't exist" do
+      assert_raise RuntimeError, fn ->
+        PacketReplay.pause_replay("nonexistent_user")
+      end
+    end
+  end
+
+  describe "resume_replay/1" do
+    test "resumes a paused replay session", %{user_id: user_id, bounds: bounds} do
+      {:ok, _pid} = PacketReplay.start_replay(user_id: user_id, bounds: bounds)
+
+      # First pause it
+      :ok = PacketReplay.pause_replay(user_id)
+      info = PacketReplay.get_replay_info(user_id)
+      assert info.paused == true
+
+      # Then resume it
+      assert :ok = PacketReplay.resume_replay(user_id)
+
+      info = PacketReplay.get_replay_info(user_id)
+      assert info.paused == false
+
+      # Clean up
+      PacketReplay.stop_replay(user_id)
+    end
+
+    test "acknowledges resume on already running session", %{user_id: user_id, bounds: bounds} do
+      {:ok, _pid} = PacketReplay.start_replay(user_id: user_id, bounds: bounds)
+
+      # Resume without pausing first
+      assert :ok = PacketReplay.resume_replay(user_id)
+
+      info = PacketReplay.get_replay_info(user_id)
+      assert info.paused == false
+
+      # Clean up
+      PacketReplay.stop_replay(user_id)
+    end
+  end
+
+  describe "set_replay_speed/2" do
+    test "sets replay speed", %{user_id: user_id, bounds: bounds} do
+      {:ok, _pid} = PacketReplay.start_replay(user_id: user_id, bounds: bounds)
+
+      assert :ok = PacketReplay.set_replay_speed(user_id, 10.0)
+
+      info = PacketReplay.get_replay_info(user_id)
+      assert info.replay_speed == 10.0
+
+      # Clean up
+      PacketReplay.stop_replay(user_id)
+    end
+
+    test "validates speed is positive number" do
+      user_id = "test_user"
+
+      # These should raise function clause errors
+      assert_raise FunctionClauseError, fn ->
+        PacketReplay.set_replay_speed(user_id, 0)
+      end
+
+      assert_raise FunctionClauseError, fn ->
+        PacketReplay.set_replay_speed(user_id, -1.0)
+      end
+
+      assert_raise FunctionClauseError, fn ->
+        PacketReplay.set_replay_speed(user_id, "invalid")
+      end
+    end
+  end
+
+  describe "update_filters/2" do
+    test "updates filters and restarts replay", %{user_id: user_id, bounds: bounds} do
+      {:ok, _pid} = PacketReplay.start_replay(user_id: user_id, bounds: bounds)
+
+      new_filters = [callsign: "N1CALL", limit: 2000]
+      assert :ok = PacketReplay.update_filters(user_id, new_filters)
+
+      info = PacketReplay.get_replay_info(user_id)
+      assert info.callsign == "N1CALL"
+
+      # Clean up
+      PacketReplay.stop_replay(user_id)
+    end
+
+    test "validates bounds format in filters", %{user_id: user_id, bounds: bounds} do
+      {:ok, _pid} = PacketReplay.start_replay(user_id: user_id, bounds: bounds)
+
+      # Valid bounds update
+      new_bounds = [-75.0, 39.0, -72.0, 42.0]
+      assert :ok = PacketReplay.update_filters(user_id, bounds: new_bounds)
+
+      info = PacketReplay.get_replay_info(user_id)
+      assert info.bounds == new_bounds
+
+      # Invalid bounds should keep old bounds
+      assert :ok = PacketReplay.update_filters(user_id, bounds: "invalid")
+
+      info = PacketReplay.get_replay_info(user_id)
+      # Should keep the valid bounds
+      assert info.bounds == new_bounds
+
+      # Clean up
+      PacketReplay.stop_replay(user_id)
+    end
+
+    test "validates filters must be a list" do
+      user_id = "test_user"
+
+      assert_raise FunctionClauseError, fn ->
+        PacketReplay.update_filters(user_id, %{callsign: "N0CALL"})
+      end
+    end
+  end
+
+  describe "get_replay_info/1" do
+    test "returns replay session information", %{user_id: user_id, bounds: bounds} do
+      start_time = DateTime.add(DateTime.utc_now(), -1800, :second)
+      end_time = DateTime.utc_now()
+
+      opts = [
+        user_id: user_id,
+        bounds: bounds,
+        callsign: "N0CALL",
+        start_time: start_time,
+        end_time: end_time,
+        replay_speed: 3.0,
+        limit: 2500,
+        with_position: true
+      ]
+
+      {:ok, _pid} = PacketReplay.start_replay(opts)
+
+      info = PacketReplay.get_replay_info(user_id)
+
+      assert info.user_id == user_id
+      assert info.bounds == bounds
+      assert info.callsign == "N0CALL"
+      assert info.start_time == start_time
+      assert info.end_time == end_time
+      assert info.replay_speed == 3.0
+      assert info.with_position == true
+      assert info.packets_sent == 0
+      assert info.paused == false
+      assert %DateTime{} = info.replay_started_at
+
+      # Clean up
+      PacketReplay.stop_replay(user_id)
+    end
+  end
+
+  describe "init/1" do
+    test "initializes with default values", %{user_id: user_id, bounds: bounds} do
+      opts = [user_id: user_id, bounds: bounds]
+
+      assert {:ok, state} = PacketReplay.init(opts)
+
+      assert state.user_id == user_id
+      assert state.bounds == bounds
+      # default
+      assert state.replay_speed == 5.0
+      # default
+      assert state.limit == 5000
+      # default
+      assert state.with_position == true
+      assert state.paused == false
+      assert state.packets_sent == 0
+      assert is_nil(state.callsign)
+      assert is_nil(state.region)
+      assert is_nil(state.replay_timer)
+      assert is_nil(state.last_packet_time)
+      assert %DateTime{} = state.start_time
+      assert %DateTime{} = state.end_time
+      assert %DateTime{} = state.replay_started_at
+    end
+
+    test "respects custom options", %{user_id: user_id, bounds: bounds} do
+      start_time = DateTime.add(DateTime.utc_now(), -1800, :second)
+      end_time = DateTime.utc_now()
+
+      opts = [
+        user_id: user_id,
+        bounds: bounds,
+        callsign: "N0CALL",
+        start_time: start_time,
+        end_time: end_time,
+        replay_speed: 2.0,
+        limit: 1000,
+        with_position: false
+      ]
+
+      assert {:ok, state} = PacketReplay.init(opts)
+
+      assert state.callsign == "N0CALL"
+      assert state.start_time == start_time
+      assert state.end_time == end_time
+      assert state.replay_speed == 2.0
+      assert state.limit == 1000
+      assert state.with_position == false
+    end
+
+    test "limits start_time to 1 hour ago maximum", %{user_id: user_id, bounds: bounds} do
+      # Try to set start time to 2 hours ago
+      old_start_time = DateTime.add(DateTime.utc_now(), -7200, :second)
+
+      opts = [
+        user_id: user_id,
+        bounds: bounds,
+        start_time: old_start_time
+      ]
+
+      assert {:ok, state} = PacketReplay.init(opts)
+
+      # Should be limited to 1 hour ago (3600 seconds)
+      one_hour_ago = DateTime.add(DateTime.utc_now(), -3600, :second)
+      assert DateTime.diff(state.start_time, one_hour_ago, :second) >= -10
+    end
+
+    test "sets replay topic correctly", %{user_id: user_id, bounds: bounds} do
+      opts = [user_id: user_id, bounds: bounds]
+
+      assert {:ok, state} = PacketReplay.init(opts)
+
+      assert state.replay_topic == "replay:#{user_id}"
+    end
+  end
+
+  describe "handle_info(:start_replay)" do
+    test "handles start_replay message with mock packets", %{mock_packet: mock_packet} do
+      # Set up mock expectations
+      MockPackets
+      |> expect(:get_historical_packet_count, fn _opts -> 1 end)
+      |> expect(:stream_packets_for_replay, fn _opts ->
+        Stream.unfold([{0.1, mock_packet}], fn
+          [packet | rest] -> {packet, rest}
+          [] -> nil
+        end)
+      end)
+
+      user_id = "test_user"
+      bounds = [-74.0, 40.0, -73.0, 41.0]
+
+      state = %{
+        user_id: user_id,
+        replay_topic: "replay:#{user_id}",
+        replay_speed: 5.0,
+        start_time: DateTime.add(DateTime.utc_now(), -3600, :second),
+        end_time: DateTime.utc_now(),
+        region: nil,
+        bounds: bounds,
+        callsign: nil,
+        with_position: true,
+        limit: 5000,
+        paused: false,
+        packets_sent: 0,
+        replay_started_at: DateTime.utc_now(),
+        replay_timer: nil,
+        last_packet_time: nil
+      }
+
+      # Subscribe to the broadcast topic to verify messages
+      Endpoint.subscribe("replay:#{user_id}")
+
+      result = PacketReplay.handle_info(:start_replay, state)
+
+      assert {:noreply, new_state} = result
+      assert new_state.last_packet_time == mock_packet.received_at
+      assert is_reference(new_state.replay_timer)
+
+      # Should have received broadcast
+      assert_receive %Broadcast{
+        topic: "replay:" <> _,
+        event: "replay_started"
+      }
+    end
+
+    test "handles empty packet stream", %{user_id: user_id, bounds: bounds} do
+      # Set up mock expectations for empty stream
+      MockPackets
+      |> expect(:get_historical_packet_count, fn _opts -> 0 end)
+      |> expect(:stream_packets_for_replay, fn _opts ->
+        Stream.unfold([], fn
+          [] -> nil
+        end)
+      end)
+
+      state = %{
+        user_id: user_id,
+        replay_topic: "replay:#{user_id}",
+        replay_speed: 5.0,
+        start_time: DateTime.add(DateTime.utc_now(), -3600, :second),
+        end_time: DateTime.utc_now(),
+        region: nil,
+        bounds: bounds,
+        callsign: nil,
+        with_position: true,
+        limit: 5000,
+        paused: false,
+        packets_sent: 0,
+        replay_started_at: DateTime.utc_now(),
+        replay_timer: nil,
+        last_packet_time: nil
+      }
+
+      # Subscribe to the broadcast topic
+      Endpoint.subscribe("replay:#{user_id}")
+
+      result = PacketReplay.handle_info(:start_replay, state)
+
+      assert {:stop, :normal, ^state} = result
+
+      # Should have received completion broadcast
+      assert_receive %Broadcast{
+        topic: "replay:" <> _,
+        event: "replay_complete",
+        payload: %{packets_sent: 0, message: "No matching packets found for replay"}
+      }
+    end
+  end
+
+  describe "handle_info({:send_packet, packet, stream})" do
+    test "reschedules packet when paused", %{mock_packet: mock_packet} do
+      stream = Stream.unfold([], fn _ -> nil end)
+
+      state = %{
+        user_id: "test_user",
+        replay_topic: "replay:test_user",
+        paused: true,
+        replay_timer: nil,
+        packets_sent: 0,
+        last_packet_time: nil
+      }
+
+      result = PacketReplay.handle_info({:send_packet, mock_packet, stream}, state)
+
+      assert {:noreply, new_state} = result
+      assert is_reference(new_state.replay_timer)
+    end
+
+    test "broadcasts packet and schedules next when not paused", %{mock_packet: mock_packet} do
+      next_packet = %{mock_packet | id: "test_packet_2"}
+
+      stream =
+        Stream.unfold([{0.1, next_packet}], fn
+          [packet | rest] -> {packet, rest}
+          [] -> nil
+        end)
+
+      state = %{
+        user_id: "test_user",
+        replay_topic: "replay:test_user",
+        paused: false,
+        replay_timer: nil,
+        packets_sent: 0,
+        last_packet_time: nil
+      }
+
+      # Subscribe to broadcasts
+      Endpoint.subscribe("replay:test_user")
+
+      result = PacketReplay.handle_info({:send_packet, mock_packet, stream}, state)
+
+      assert {:noreply, new_state} = result
+      assert new_state.packets_sent == 1
+      assert new_state.last_packet_time == next_packet.received_at
+      assert is_reference(new_state.replay_timer)
+
+      # Should have received packet broadcast
+      assert_receive %Broadcast{
+        event: "historical_packet",
+        payload: %{is_historical: true}
+      }
+    end
+
+    test "completes replay when no more packets", %{mock_packet: mock_packet} do
+      # Empty stream - no more packets
+      stream = Stream.unfold([], fn _ -> nil end)
+
+      state = %{
+        user_id: "test_user",
+        replay_topic: "replay:test_user",
+        paused: false,
+        replay_timer: nil,
+        packets_sent: 5,
+        last_packet_time: nil
+      }
+
+      # Subscribe to broadcasts
+      Endpoint.subscribe("replay:test_user")
+
+      result = PacketReplay.handle_info({:send_packet, mock_packet, stream}, state)
+
+      assert {:stop, :normal, new_state} = result
+      assert new_state.packets_sent == 6
+
+      # Should have received completion broadcast
+      assert_receive %Broadcast{
+        event: "replay_complete",
+        payload: %{packets_sent: 6, message: "Replay complete"}
+      }
+    end
+  end
+
+  describe "sanitize_packet_for_transport/1" do
+    test "converts packet to JSON-safe format" do
+      packet = %{
+        __meta__: %{},
+        __struct__: SomeStruct,
+        id: "test",
+        received_at: ~U[2023-01-01 12:00:00Z],
+        lat: Decimal.new("40.123456"),
+        nested: %{
+          timestamp: ~N[2023-01-01 12:00:00],
+          value: Decimal.new("1.23")
+        },
+        list: [~U[2023-01-01 12:00:00Z], Decimal.new("4.56")]
+      }
+
+      result = PacketReplay.sanitize_packet_for_transport(packet)
+
+      # Should drop meta fields
+      refute Map.has_key?(result, :__meta__)
+      refute Map.has_key?(result, :__struct__)
+
+      # Should preserve normal fields
+      assert result.id == "test"
+
+      # Should convert DateTime to ISO string
+      assert result.received_at == "2023-01-01T12:00:00Z"
+
+      # Should convert Decimal to float
+      assert result.lat == 40.123456
+
+      # Should handle nested structures
+      assert result.nested.timestamp == "2023-01-01T12:00:00"
+      assert result.nested.value == 1.23
+
+      # Should handle lists
+      assert result.list == ["2023-01-01T12:00:00Z", 4.56]
+    end
+
+    test "handles packets without special types" do
+      packet = %{
+        id: "simple",
+        name: "test",
+        count: 42,
+        active: true
+      }
+
+      result = PacketReplay.sanitize_packet_for_transport(packet)
+
+      assert result == %{
+               id: "simple",
+               name: "test",
+               count: 42,
+               active: true
+             }
+    end
+  end
+
+  describe "via_tuple/1" do
+    test "generates correct registry tuple" do
+      user_id = "test_user_123"
+
+      result = PacketReplay.via_tuple(user_id)
+
+      assert result == {:via, Registry, {Aprs.ReplayRegistry, "replay:test_user_123"}}
+    end
+  end
+
+  describe "terminate/2" do
+    test "cleans up timers and broadcasts stop message" do
+      timer_ref = make_ref()
+
+      state = %{
+        user_id: "test_user",
+        replay_topic: "replay:test_user",
+        replay_timer: timer_ref,
+        packets_sent: 10
+      }
+
+      # Subscribe to broadcasts
+      Endpoint.subscribe("replay:test_user")
+
+      result = PacketReplay.terminate(:normal, state)
+
+      assert result == :ok
+
+      # Should have received stop broadcast
+      assert_receive %Broadcast{
+        event: "replay_stopped",
+        payload: %{packets_sent: 10, message: "Replay stopped"}
+      }
+    end
+
+    test "handles state without timer" do
+      state = %{
+        user_id: "test_user",
+        replay_topic: "replay:test_user",
+        replay_timer: nil,
+        packets_sent: 0
+      }
+
+      # Subscribe to broadcasts
+      Endpoint.subscribe("replay:test_user")
+
+      result = PacketReplay.terminate(:shutdown, state)
+
+      assert result == :ok
+
+      # Should still broadcast stop message
+      assert_receive %Broadcast{
+        event: "replay_stopped"
+      }
+    end
+  end
+
+  describe "integration tests" do
+    test "full replay lifecycle", %{user_id: user_id, bounds: bounds, mock_packet: mock_packet} do
+      # Set up mock for full lifecycle
+      MockPackets
+      |> expect(:get_historical_packet_count, fn _opts -> 1 end)
+      |> expect(:stream_packets_for_replay, fn _opts ->
+        # Single packet stream
+        Stream.unfold([{0.001, mock_packet}], fn
+          [packet | rest] -> {packet, rest}
+          [] -> nil
+        end)
+      end)
+
+      # Start replay
+      {:ok, pid} = PacketReplay.start_replay(user_id: user_id, bounds: bounds)
+
+      # Subscribe to events
+      Endpoint.subscribe("replay:#{user_id}")
+
+      # Should receive start event
+      assert_receive %Broadcast{
+                       event: "replay_started"
+                     },
+                     1000
+
+      # Should receive packet event quickly (1ms delay)
+      assert_receive %Broadcast{
+                       event: "historical_packet"
+                     },
+                     1000
+
+      # Should receive completion event
+      assert_receive %Broadcast{
+                       event: "replay_complete"
+                     },
+                     1000
+
+      # Process should terminate
+      Process.sleep(50)
+      refute Process.alive?(pid)
+    end
+
+    test "pause and resume functionality", %{user_id: user_id, bounds: bounds} do
+      {:ok, pid} = PacketReplay.start_replay(user_id: user_id, bounds: bounds)
+
+      # Subscribe to events
+      Endpoint.subscribe("replay:#{user_id}")
+
+      # Pause
+      :ok = PacketReplay.pause_replay(user_id)
+
+      assert_receive %Broadcast{
+        event: "replay_paused"
+      }
+
+      info = PacketReplay.get_replay_info(user_id)
+      assert info.paused == true
+
+      # Resume
+      :ok = PacketReplay.resume_replay(user_id)
+
+      assert_receive %Broadcast{
+        event: "replay_resumed"
+      }
+
+      info = PacketReplay.get_replay_info(user_id)
+      assert info.paused == false
+
+      # Clean up
+      GenServer.stop(pid)
+    end
+  end
+end