diff --git a/test/test_nmt.py b/test/test_nmt.py
index 50db1187..c24e8d96 100644
--- a/test/test_nmt.py
+++ b/test/test_nmt.py
@@ -1,21 +1,139 @@
 import time
 import unittest
 
+import can
 import canopen
+from canopen.nmt import COMMAND_TO_STATE, NMT_STATES, NMT_COMMANDS, NmtError
 from .util import SAMPLE_EDS
 
 
+class TestNmtBase(unittest.TestCase):
+    def setUp(self):
+        node_id = 2
+        self.node_id = node_id
+        self.nmt = canopen.nmt.NmtBase(node_id)
+
+    def test_send_command(self):
+        dataset = (
+            "OPERATIONAL",
+            "PRE-OPERATIONAL",
+            "SLEEP",
+            "STANDBY",
+            "STOPPED",
+        )
+        for cmd in dataset:
+            with self.subTest(cmd=cmd):
+                code = NMT_COMMANDS[cmd]
+                self.nmt.send_command(code)
+                expected = NMT_STATES[COMMAND_TO_STATE[code]]
+                self.assertEqual(self.nmt.state, expected)
+
+    def test_state_getset(self):
+        for state in NMT_STATES.values():
+            with self.subTest(state=state):
+                self.nmt.state = state
+                self.assertEqual(self.nmt.state, state)
+
+    def test_state_set_invalid(self):
+        with self.assertRaisesRegex(ValueError, "INVALID"):
+            self.nmt.state = "INVALID"
+
+
+class TestNmtMaster(unittest.TestCase):
+    NODE_ID = 2
+    COB_ID = 0x700 + NODE_ID
+    PERIOD = 0.01
+    TIMEOUT = PERIOD * 2
+
+    def setUp(self):
+        bus = can.ThreadSafeBus(
+            interface="virtual",
+            channel="test",
+            receive_own_messages=True,
+        )
+        net = canopen.Network(bus)
+        net.connect()
+        with self.assertLogs():
+            node = net.add_node(self.NODE_ID, SAMPLE_EDS)
+
+        self.bus = bus
+        self.net = net
+        self.node = node
+
+    def tearDown(self):
+        self.net.disconnect()
+
+    def test_nmt_master_no_heartbeat(self):
+        with self.assertRaisesRegex(NmtError, "heartbeat"):
+            self.node.nmt.wait_for_heartbeat(self.TIMEOUT)
+        with self.assertRaisesRegex(NmtError, "boot-up"):
+            self.node.nmt.wait_for_bootup(self.TIMEOUT)
+
+    def test_nmt_master_on_heartbeat(self):
+        # Skip the special INITIALISING case.
+        for code in [st for st in NMT_STATES if st != 0]:
+            with self.subTest(code=code):
+                task = self.net.send_periodic(self.COB_ID, [code], self.PERIOD)
+                try:
+                    actual = self.node.nmt.wait_for_heartbeat(self.TIMEOUT)
+                finally:
+                    task.stop()
+                expected = NMT_STATES[code]
+                self.assertEqual(actual, expected)
+
+    def test_nmt_master_on_heartbeat_initialising(self):
+        task = self.net.send_periodic(self.COB_ID, [0], self.PERIOD)
+        self.addCleanup(task.stop)
+        self.node.nmt.wait_for_bootup(self.TIMEOUT)
+        state = self.node.nmt.wait_for_heartbeat(self.TIMEOUT)
+        self.assertEqual(state, "PRE-OPERATIONAL")
+
+    @unittest.expectedFailure
+    def test_nmt_master_on_heartbeat_unknown_state(self):
+        task = self.net.send_periodic(self.COB_ID, [0xcb], self.PERIOD)
+        self.addCleanup(task.stop)
+        state = self.node.nmt.wait_for_heartbeat(self.TIMEOUT)
+        # Expect the high bit to be masked out, and and unknown state string to
+        # be returned.
+        self.assertEqual(state, "UNKNOWN STATE '75'")
+
+    def test_nmt_master_add_heartbeat_callback(self):
+        from threading import Event
+        event = Event()
+        state = None
+        def hook(st):
+            nonlocal state
+            state = st
+            event.set()
+        self.node.nmt.add_heartbeat_callback(hook)
+        self.net.send_message(self.COB_ID, bytes([127]))
+        self.assertTrue(event.wait(self.TIMEOUT))
+        self.assertEqual(state, 127)
+
+    def test_nmt_master_node_guarding(self):
+        self.node.nmt.start_node_guarding(self.PERIOD)
+        msg = self.bus.recv(self.TIMEOUT)
+        self.assertIsNotNone(msg)
+        self.assertEqual(msg.arbitration_id, self.COB_ID)
+        self.assertEqual(msg.dlc, 0)
+
+        self.node.nmt.stop_node_guarding()
+        self.assertIsNone(self.bus.recv(self.TIMEOUT))
+
+
 class TestNmtSlave(unittest.TestCase):
     def setUp(self):
         self.network1 = canopen.Network()
         self.network1.connect("test", interface="virtual")
-        self.remote_node = self.network1.add_node(2, SAMPLE_EDS)
+        with self.assertLogs():
+            self.remote_node = self.network1.add_node(2, SAMPLE_EDS)
 
         self.network2 = canopen.Network()
         self.network2.connect("test", interface="virtual")
-        self.local_node = self.network2.create_node(2, SAMPLE_EDS)
-        self.remote_node2 = self.network1.add_node(3, SAMPLE_EDS)
-        self.local_node2 = self.network2.create_node(3, SAMPLE_EDS)
+        with self.assertLogs():
+            self.local_node = self.network2.create_node(2, SAMPLE_EDS)
+            self.remote_node2 = self.network1.add_node(3, SAMPLE_EDS)
+            self.local_node2 = self.network2.create_node(3, SAMPLE_EDS)
 
     def tearDown(self):
         self.network1.disconnect()