diff --git a/tests/test_peer/test_connection.py b/tests/test_peer/test_connection.py
index ba9e658..b36ca0c 100644
--- a/tests/test_peer/test_connection.py
+++ b/tests/test_peer/test_connection.py
@@ -12,6 +12,8 @@
     AX25DisconnectModeFrame,
     AX25FrameRejectFrame,
     AX25UnnumberedAcknowledgeFrame,
+    AX25UnnumberedInformationFrame,
+    AX25RawFrame,
     AX25TestFrame,
     AX25SetAsyncBalancedModeFrame,
     AX25SetAsyncBalancedModeExtendedFrame,
@@ -295,6 +297,304 @@ def _on_receive_ua():
     assert count == dict(ua=1)
 
 
+def test_recv_ui():
+    """
+    Test that UI is emitted by the received frame signal.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path("VK4RZB"),
+        locked_path=True,
+    )
+
+    # Stub idle time-out handling
+    peer._reset_idle_timeout = lambda: None
+
+    # Create a handler for receiving the UI
+    rx_frames = []
+
+    def _on_receive_frame(frame, **kwargs):
+        assert "peer" in kwargs
+        assert kwargs.pop("peer") is peer
+        assert kwargs == {}
+        rx_frames.append(frame)
+
+    peer.received_frame.connect(_on_receive_frame)
+
+    # Set the state
+    peer._state = AX25PeerState.CONNECTED
+
+    # Inject a frame
+    frame = AX25UnnumberedInformationFrame(
+        destination=AX25Address("VK4MSL-1"),
+        source=AX25Address("VK4MSL"),
+        repeaters=AX25Path("VK4RZB"),
+        pid=0xF0,
+        payload=b"Testing 1 2 3 4",
+    )
+
+    peer._on_receive(frame)
+
+    # Our handler should have been called
+    assert len(rx_frames) == 1
+    assert rx_frames[0] is frame
+
+
+def test_recv_raw_noconn():
+    """
+    Test that a raw frame without a connection triggers a DM frame.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path("VK4RZB"),
+        locked_path=True,
+    )
+
+    # Stub idle time-out handling
+    peer._reset_idle_timeout = lambda: None
+
+    # Stub _send_dm
+    count = dict(send_dm=0)
+
+    def _send_dm():
+        count["send_dm"] += 1
+
+    peer._send_dm = _send_dm
+
+    # Set the state
+    peer._state = AX25PeerState.DISCONNECTED
+
+    # Inject a frame
+    peer._on_receive(
+        AX25RawFrame(
+            destination=AX25Address("VK4MSL-1"),
+            source=AX25Address("VK4MSL"),
+            repeaters=AX25Path("VK4RZB"),
+            payload=b"\x00\x00Testing 1 2 3 4",
+        )
+    )
+
+
+def test_recv_raw_mod8_iframe():
+    """
+    Test that a I-frame with Mod8 connection is handled.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path("VK4RZB"),
+        locked_path=True,
+    )
+
+    # Stub idle time-out handling
+    peer._reset_idle_timeout = lambda: None
+
+    # Stub _on_receive_iframe
+    iframes = []
+
+    def _on_receive_iframe(frame):
+        iframes.append(frame)
+
+    peer._on_receive_iframe = _on_receive_iframe
+
+    # Stub _on_receive_sframe
+    sframes = []
+
+    def _on_receive_sframe(frame):
+        sframes.append(frame)
+
+    peer._on_receive_sframe = _on_receive_sframe
+
+    # Set the state
+    peer._state = AX25PeerState.CONNECTED
+    peer._modulo = 8
+
+    # Inject a frame
+    peer._on_receive(
+        AX25RawFrame(
+            destination=AX25Address("VK4MSL-1"),
+            source=AX25Address("VK4MSL"),
+            repeaters=AX25Path("VK4RZB"),
+            payload=b"\xd4\xf0Testing 1 2 3 4",
+        )
+    )
+
+    # Our I-frame handler should have been called
+    assert len(iframes) == 1
+    assert isinstance(iframes[0], AX258BitInformationFrame)
+    assert iframes[0].pid == 0xf0
+    assert iframes[0].payload == b"Testing 1 2 3 4"
+
+    # Our S-frame handler should NOT have been called
+    assert sframes == []
+
+
+def test_recv_raw_mod128_iframe():
+    """
+    Test that a I-frame with Mod128 connection is handled.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path("VK4RZB"),
+        locked_path=True,
+    )
+
+    # Stub idle time-out handling
+    peer._reset_idle_timeout = lambda: None
+
+    # Stub _on_receive_iframe
+    iframes = []
+
+    def _on_receive_iframe(frame):
+        iframes.append(frame)
+
+    peer._on_receive_iframe = _on_receive_iframe
+
+    # Stub _on_receive_sframe
+    sframes = []
+
+    def _on_receive_sframe(frame):
+        sframes.append(frame)
+
+    peer._on_receive_sframe = _on_receive_sframe
+
+    # Set the state
+    peer._state = AX25PeerState.CONNECTED
+    peer._modulo = 128
+
+    # Inject a frame
+    peer._on_receive(
+        AX25RawFrame(
+            destination=AX25Address("VK4MSL-1"),
+            source=AX25Address("VK4MSL"),
+            repeaters=AX25Path("VK4RZB"),
+            payload=b"\x04\x0d\xf0Testing 1 2 3 4",
+        )
+    )
+
+    # Our I-frame handler should have been called
+    assert len(iframes) == 1
+    assert isinstance(iframes[0], AX2516BitInformationFrame)
+    assert iframes[0].pid == 0xf0
+    assert iframes[0].payload == b"Testing 1 2 3 4"
+
+    # Our S-frame handler should NOT have been called
+    assert sframes == []
+
+
+def test_recv_raw_mod8_sframe():
+    """
+    Test that a S-frame with Mod8 connection is handled.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path("VK4RZB"),
+        locked_path=True,
+    )
+
+    # Stub idle time-out handling
+    peer._reset_idle_timeout = lambda: None
+
+    # Stub _on_receive_iframe
+    iframes = []
+
+    def _on_receive_iframe(frame):
+        iframes.append(frame)
+
+    peer._on_receive_iframe = _on_receive_iframe
+
+    # Stub _on_receive_sframe
+    sframes = []
+
+    def _on_receive_sframe(frame):
+        sframes.append(frame)
+
+    peer._on_receive_sframe = _on_receive_sframe
+
+    # Set the state
+    peer._state = AX25PeerState.CONNECTED
+    peer._modulo = 8
+
+    # Inject a frame
+    peer._on_receive(
+        AX25RawFrame(
+            destination=AX25Address("VK4MSL-1"),
+            source=AX25Address("VK4MSL"),
+            repeaters=AX25Path("VK4RZB"),
+            payload=b"\x41",
+        )
+    )
+
+    # Our S-frame handler should have been called
+    assert len(sframes) == 1
+    assert isinstance(sframes[0], AX258BitReceiveReadyFrame)
+
+    # Our I-frame handler should NOT have been called
+    assert iframes == []
+
+
+def test_recv_raw_mod128_sframe():
+    """
+    Test that a S-frame with Mod128 connection is handled.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path("VK4RZB"),
+        locked_path=True,
+    )
+
+    # Stub idle time-out handling
+    peer._reset_idle_timeout = lambda: None
+
+    # Stub _on_receive_iframe
+    iframes = []
+
+    def _on_receive_iframe(frame):
+        iframes.append(frame)
+
+    peer._on_receive_iframe = _on_receive_iframe
+
+    # Stub _on_receive_sframe
+    sframes = []
+
+    def _on_receive_sframe(frame):
+        sframes.append(frame)
+
+    peer._on_receive_sframe = _on_receive_sframe
+
+    # Set the state
+    peer._state = AX25PeerState.CONNECTED
+    peer._modulo = 128
+
+    # Inject a frame
+    peer._on_receive(
+        AX25RawFrame(
+            destination=AX25Address("VK4MSL-1"),
+            source=AX25Address("VK4MSL"),
+            repeaters=AX25Path("VK4RZB"),
+            payload=b"\x01\x5c",
+        )
+    )
+
+    # Our S-frame handler should have been called
+    assert len(sframes) == 1
+    assert isinstance(sframes[0], AX2516BitReceiveReadyFrame)
+
+    # Our I-frame handler should NOT have been called
+    assert iframes == []
+
+
 def test_recv_disc():
     """
     Test that DISC is handled.