diff --git a/src/allmydata/node.py b/src/allmydata/node.py
index d93fb5324..c257868b4 100644
--- a/src/allmydata/node.py
+++ b/src/allmydata/node.py
@@ -401,6 +401,11 @@ class Node(service.MultiService):
                 if port in ("0", "tcp:0"):
                     raise ValueError("tub.port cannot be 0: you must choose")
                 if port == "listen:i2p":
+                    # the I2P provider will read its section of tahoe.cfg and
+                    # return either a fully-formed Endpoint, or a descriptor
+                    # that will create one, so we don't have to stuff all the
+                    # options into the tub.port string (which would need a lot
+                    # of escaping)
                     port_or_endpoint = self._i2p_provider.get_listener()
                 elif port == "listen:tor":
                     port_or_endpoint = self._tor_provider.get_listener()
diff --git a/src/allmydata/test/test_i2p_provider.py b/src/allmydata/test/test_i2p_provider.py
index dc328476e..081be0fc7 100644
--- a/src/allmydata/test/test_i2p_provider.py
+++ b/src/allmydata/test/test_i2p_provider.py
@@ -294,8 +294,13 @@ class Provider(unittest.TestCase):
         self.assertIs(h, handler)
         i2p.default.assert_called_with(reactor, keyfile=None)
 
-class Provider_Listener(unittest.TestCase):
+class ProviderListener(unittest.TestCase):
     def test_listener(self):
+        """Does the I2P Provider object's get_listener() method correctly
+        convert the [i2p] section of tahoe.cfg into an
+        endpoint/descriptor?
+        """
+
         i2p = mock.Mock()
         handler = object()
         i2p.local_i2p = mock.Mock(return_value=handler)
diff --git a/src/allmydata/test/test_tor_provider.py b/src/allmydata/test/test_tor_provider.py
index a40698f86..0a1f589bf 100644
--- a/src/allmydata/test/test_tor_provider.py
+++ b/src/allmydata/test/test_tor_provider.py
@@ -393,8 +393,12 @@ class Provider(unittest.TestCase):
         self.assertIs(h, handler)
         tor.default_socks.assert_called_with()
 
-class Provider_Listener(unittest.TestCase):
+class ProviderListener(unittest.TestCase):
     def test_listener(self):
+        """Does the Tor Provider object's get_listener() method correctly
+        convert the [tor] section of tahoe.cfg into an
+        endpoint/descriptor?
+        """
         tor = mock.Mock()
         handler = object()
         tor.socks_endpoint = mock.Mock(return_value=handler)