diff --git a/tests/test_if_spectator.py b/tests/test_if_spectator.py
new file mode 100644
index 0000000..321a454
--- /dev/null
+++ b/tests/test_if_spectator.py
@@ -0,0 +1,195 @@
+"""Tests for spectator broadcasting in IF mode."""
+
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from mudlib.if_session import IFResponse, IFSession
+from mudlib.player import Player, players
+
+
+@pytest.fixture
+def mock_writer():
+    writer = MagicMock()
+    writer.write = MagicMock()
+    writer.drain = AsyncMock()
+    return writer
+
+
+@pytest.fixture
+def mock_reader():
+    return MagicMock()
+
+
+@pytest.fixture(autouse=True)
+def clear_players():
+    """Clear players registry before and after each test."""
+    players.clear()
+    yield
+    players.clear()
+
+
+@pytest.fixture
+def player_a(mock_reader, mock_writer):
+    """Player A at (5, 5) who will be playing IF."""
+    return Player(
+        name="PlayerA", x=5, y=5, reader=mock_reader, writer=mock_writer
+    )
+
+
+@pytest.fixture
+def player_b(mock_reader, mock_writer):
+    """Player B at (5, 5) who will be spectating."""
+    return Player(
+        name="PlayerB", x=5, y=5, reader=mock_reader, writer=mock_writer
+    )
+
+
+@pytest.fixture
+def player_c(mock_reader, mock_writer):
+    """Player C at different coords (10, 10)."""
+    return Player(
+        name="PlayerC", x=10, y=10, reader=mock_reader, writer=mock_writer
+    )
+
+
+@pytest.mark.asyncio
+async def test_spectator_sees_if_output(player_a, player_b):
+    """Spectator at same location sees IF output with header and input."""
+    # Register both players
+    players[player_a.name] = player_a
+    players[player_b.name] = player_b
+
+    # Create mock IF session for player A
+    mock_session = MagicMock()
+    mock_session.handle_input = AsyncMock(
+        return_value=IFResponse(
+            output="Opening the small mailbox reveals a leaflet.", done=False
+        )
+    )
+    player_a.if_session = mock_session
+    player_a.mode_stack.append("if")
+
+    # Import the broadcast function (will be created in implementation)
+    from mudlib.if_session import broadcast_to_spectators
+
+    # Player A sends input
+    command = "open mailbox"
+    response = await player_a.if_session.handle_input(command)
+    await player_a.send(response.output)
+
+    # Broadcast to spectators
+    spectator_msg = (
+        f"[{player_a.name}'s terminal]\r\n"
+        f"> {command}\r\n"
+        f"{response.output}"
+    )
+    await broadcast_to_spectators(player_a, spectator_msg)
+
+    # Player B should have received the message
+    assert player_b.writer.write.called
+    calls = player_b.writer.write.call_args_list
+    sent_text = "".join(call[0][0] for call in calls)
+    assert "[PlayerA's terminal]" in sent_text
+    assert "> open mailbox" in sent_text
+    assert "Opening the small mailbox reveals a leaflet." in sent_text
+
+
+@pytest.mark.asyncio
+async def test_spectator_not_on_same_tile_sees_nothing(player_a, player_c):
+    """Spectator at different location does not see IF output."""
+    # Register both players (player_c is at different coords)
+    players[player_a.name] = player_a
+    players[player_c.name] = player_c
+
+    # Create mock IF session for player A
+    mock_session = MagicMock()
+    mock_session.handle_input = AsyncMock(
+        return_value=IFResponse(output="You open the door.", done=False)
+    )
+    player_a.if_session = mock_session
+    player_a.mode_stack.append("if")
+
+    from mudlib.if_session import broadcast_to_spectators
+
+    # Player A sends input
+    command = "open door"
+    response = await player_a.if_session.handle_input(command)
+    await player_a.send(response.output)
+
+    # Broadcast to spectators
+    spectator_msg = (
+        f"[{player_a.name}'s terminal]\r\n"
+        f"> {command}\r\n"
+        f"{response.output}"
+    )
+    await broadcast_to_spectators(player_a, spectator_msg)
+
+    # Player C should NOT have received anything
+    assert not player_c.writer.write.called
+
+
+@pytest.mark.asyncio
+async def test_spectator_sees_game_start(player_a, player_b):
+    """Spectator sees formatted intro text when player starts game."""
+    # Register both players
+    players[player_a.name] = player_a
+    players[player_b.name] = player_b
+
+    from mudlib.if_session import broadcast_to_spectators
+
+    # Simulate game start with intro text
+    intro = "ZORK I: The Great Underground Empire\nCopyright (c) 1981"
+    spectator_msg = f"[{player_a.name}'s terminal]\r\n{intro}\r\n"
+
+    await broadcast_to_spectators(player_a, spectator_msg)
+
+    # Player B should see the intro
+    assert player_b.writer.write.called
+    calls = player_b.writer.write.call_args_list
+    sent_text = "".join(call[0][0] for call in calls)
+    assert "[PlayerA's terminal]" in sent_text
+    assert "ZORK I: The Great Underground Empire" in sent_text
+
+
+@pytest.mark.asyncio
+async def test_broadcast_to_spectators_skips_self(player_a, player_b):
+    """broadcast_to_spectators does not send to the playing player."""
+    # Register both players
+    players[player_a.name] = player_a
+    players[player_b.name] = player_b
+
+    from mudlib.if_session import broadcast_to_spectators
+
+    message = "[PlayerA's terminal]\r\n> look\r\nYou see a room.\r\n"
+    await broadcast_to_spectators(player_a, message)
+
+    # Player A should NOT have received the message
+    assert not player_a.writer.write.called
+    # Player B should have received it
+    assert player_b.writer.write.called
+
+
+@pytest.mark.asyncio
+async def test_multiple_spectators(player_a, player_b, mock_reader, mock_writer):
+    """Multiple spectators at same location all see IF output."""
+    # Create a third player at same location
+    player_d = Player(
+        name="PlayerD", x=5, y=5, reader=mock_reader, writer=mock_writer
+    )
+
+    # Register all players
+    players[player_a.name] = player_a
+    players[player_b.name] = player_b
+    players[player_d.name] = player_d
+
+    from mudlib.if_session import broadcast_to_spectators
+
+    message = "[PlayerA's terminal]\r\n> inventory\r\nYou are empty-handed.\r\n"
+    await broadcast_to_spectators(player_a, message)
+
+    # Both spectators should see the message
+    assert player_b.writer.write.called
+    assert player_d.writer.write.called
+    # Player A should not
+    assert not player_a.writer.write.called