diff --git a/irctest/cases.py b/irctest/cases.py
index b26f310..c050ed5 100644
--- a/irctest/cases.py
+++ b/irctest/cases.py
@@ -308,15 +308,23 @@ class BaseServerTestCase(_IrcTestCase):
             m = self.getMessage(client, synchronize=False)
             if m.command == '001':
                 return m
-    def connectClient(self, nick, name=None, capabilities=None):
+    def connectClient(self, nick, name=None, capabilities=None,
+            skip_if_cap_nak=False):
         client = self.addClient(name)
         if capabilities is not None:
             self.sendLine(client, 'CAP REQ :{}'.format(' '.join(capabilities)))
             m = self.getRegistrationMessage(client)
-            self.assertMessageEqual(m, command='CAP',
-                    fail_msg='Expected CAP ACK, got: {msg}')
-            self.assertEqual(m.params[1], 'ACK', m,
-                    fail_msg='Expected CAP ACK, got: {msg}')
+            try:
+                self.assertMessageEqual(m, command='CAP',
+                        fail_msg='Expected CAP ACK, got: {msg}')
+                self.assertEqual(m.params[1], 'ACK', m,
+                        fail_msg='Expected CAP ACK, got: {msg}')
+            except AssertionError:
+                if skip_if_cap_nak:
+                    raise runner.NotImplementedByController(
+                            ', '.join(capabilities))
+                else:
+                    raise
             self.sendLine(client, 'CAP END')
         self.sendLine(client, 'NICK {}'.format(nick))
         self.sendLine(client, 'USER username * * :Realname')
diff --git a/irctest/server_tests/test_account_tag.py b/irctest/server_tests/test_account_tag.py
index d970209..582e4ea 100644
--- a/irctest/server_tests/test_account_tag.py
+++ b/irctest/server_tests/test_account_tag.py
@@ -21,7 +21,7 @@ class AccountTagTestCase(cases.BaseServerTestCase, cases.OptionalityHelper):
         m = self.getMessage(2, filter_pred=lambda m:m.command != 'NOTICE')
         self.assertMessageEqual(m, command='900',
                 fail_msg='Did not send 900 after correct SASL authentication.')
-        self.sendLine(2, 'USER f * * :*')
+        self.sendLine(2, 'USER f * * :Realname')
         self.sendLine(2, 'NICK {}'.format(nick))
         self.sendLine(2, 'CAP END')
         self.skipToWelcome(2)
@@ -29,10 +29,8 @@ class AccountTagTestCase(cases.BaseServerTestCase, cases.OptionalityHelper):
     @cases.SpecificationSelector.requiredBySpecification('IRCv3.2')
     @cases.OptionalityHelper.skipUnlessHasMechanism('PLAIN')
     def testPrivmsg(self):
-        try:
-            self.connectClient('foo', capabilities=['account-tag'])
-        except AssertionError:
-            raise NotImplementedByController('account-tag')
+        self.connectClient('foo', capabilities=['account-tag'],
+                skip_if_cap_nak=True)
         self.getMessages(1)
         self.controller.registerUser(self, 'jilles', 'sesame')
         self.connectRegisteredClient('bar')
@@ -54,10 +52,8 @@ class AccountTagTestCase(cases.BaseServerTestCase, cases.OptionalityHelper):
     @cases.SpecificationSelector.requiredBySpecification('IRCv3.2')
     @cases.OptionalityHelper.skipUnlessHasMechanism('PLAIN')
     def testMonitor(self):
-        try:
-            self.connectClient('foo', capabilities=['account-tag'])
-        except AssertionError:
-            raise NotImplementedByController('account-tag')
+        self.connectClient('foo', capabilities=['account-tag'],
+                skip_if_cap_nak=True)
         if 'MONITOR' not in self.server_support:
             raise NotImplementedByController('MONITOR')
         self.sendLine(1, 'MONITOR + bar')
diff --git a/irctest/server_tests/test_extended_join.py b/irctest/server_tests/test_extended_join.py
new file mode 100644
index 0000000..73e9c2b
--- /dev/null
+++ b/irctest/server_tests/test_extended_join.py
@@ -0,0 +1,58 @@
+"""
+<http://ircv3.net/specs/extensions/extended-join-3.1.html>
+"""
+
+from irctest import cases
+from irctest.irc_utils.message_parser import Message
+
+class MetadataTestCase(cases.BaseServerTestCase, cases.OptionalityHelper):
+    def connectRegisteredClient(self, nick):
+        self.addClient()
+        self.sendLine(2, 'CAP LS 302')
+        capabilities = self.getCapLs(2)
+        assert 'sasl' in capabilities
+        self.sendLine(2, 'AUTHENTICATE PLAIN')
+        m = self.getMessage(2, filter_pred=lambda m:m.command != 'NOTICE')
+        self.assertMessageEqual(m, command='AUTHENTICATE', params=['+'],
+                fail_msg='Sent “AUTHENTICATE PLAIN”, server should have '
+                'replied with “AUTHENTICATE +”, but instead sent: {msg}')
+        self.sendLine(2, 'AUTHENTICATE amlsbGVzAGppbGxlcwBzZXNhbWU=')
+        m = self.getMessage(2, filter_pred=lambda m:m.command != 'NOTICE')
+        self.assertMessageEqual(m, command='900',
+                fail_msg='Did not send 900 after correct SASL authentication.')
+        self.sendLine(2, 'USER f * * :Realname')
+        self.sendLine(2, 'NICK {}'.format(nick))
+        self.sendLine(2, 'CAP END')
+        self.skipToWelcome(2)
+
+    @cases.SpecificationSelector.requiredBySpecification('IRCv3.1')
+    def testNotLoggedIn(self):
+        self.connectClient('foo', capabilities=['extended-join'],
+                skip_if_cap_nak=True)
+        self.sendLine(1, 'JOIN #chan')
+        self.getMessages(1)
+        self.connectClient('bar')
+        self.sendLine(2, 'JOIN #chan')
+        m = self.getMessage(1)
+        self.assertMessageEqual(m, command='JOIN',
+                params=['#chan', '*', 'Realname'],
+                fail_msg='Expected “JOIN #chan * :Realname” after '
+                'unregistered user joined, got: {msg}')
+
+    @cases.SpecificationSelector.requiredBySpecification('IRCv3.1')
+    @cases.OptionalityHelper.skipUnlessHasMechanism('PLAIN')
+    def testNotLoggedIn(self):
+        self.connectClient('foo', capabilities=['extended-join'],
+                skip_if_cap_nak=True)
+        self.sendLine(1, 'JOIN #chan')
+        self.getMessages(1)
+
+        self.controller.registerUser(self, 'jilles', 'sesame')
+        self.connectRegisteredClient('bar')
+
+        self.sendLine(2, 'JOIN #chan')
+        m = self.getMessage(1)
+        self.assertMessageEqual(m, command='JOIN',
+                params=['#chan', 'jilles', 'Realname'],
+                fail_msg='Expected “JOIN #chan * :Realname” after '
+                'nick “bar” logged in as “jilles” joined, got: {msg}')