diff --git a/irctest/cases.py b/irctest/cases.py
index 2e2cefb..1c61dd7 100644
--- a/irctest/cases.py
+++ b/irctest/cases.py
@@ -577,7 +577,9 @@ class BaseServerTestCase(
         Returns the list of all messages received after registration,
         just like `skipToWelcome`."""
         client = self.addClient(name, show_io=show_io)
-        if capabilities is not None and 0 < len(capabilities):
+        if capabilities:
+            self.sendLine(client, "CAP LS 302")
+            m = self.getRegistrationMessage(client)
             self.sendLine(client, "CAP REQ :{}".format(" ".join(capabilities)))
             m = self.getRegistrationMessage(client)
             try:
@@ -592,12 +594,18 @@ class BaseServerTestCase(
                     raise runner.CapabilityNotSupported(" or ".join(capabilities))
                 else:
                     raise
-            self.sendLine(client, "CAP END")
         if password is not None:
             self.sendLine(client, "AUTHENTICATE PLAIN")
+            m = self.getRegistrationMessage(client)
+            self.assertMessageMatch(m, command="AUTHENTICATE", params=["+"])
             self.sendLine(client, sasl_plain_blob(account or nick, password))
+            m = self.getRegistrationMessage(client)
+            self.assertIn(m.command, ["900", "903"], str(m))
+
         self.sendLine(client, "NICK {}".format(nick))
         self.sendLine(client, "USER %s * * :Realname" % (ident,))
+        if capabilities:
+            self.sendLine(client, "CAP END")
 
         welcome = self.skipToWelcome(client)
         self.sendLine(client, "PING foo")
diff --git a/irctest/server_tests/test_account_tag.py b/irctest/server_tests/test_account_tag.py
index 321783a..0e28d84 100644
--- a/irctest/server_tests/test_account_tag.py
+++ b/irctest/server_tests/test_account_tag.py
@@ -11,8 +11,16 @@ class AccountTagTestCase(cases.BaseServerTestCase, cases.OptionalityHelper):
         self.sendLine(2, "CAP LS 302")
         capabilities = self.getCapLs(2)
         assert "sasl" in capabilities
+
+        self.sendLine(2, "USER f * * :Realname")
+        self.sendLine(2, "NICK {}".format(nick))
+        self.sendLine(2, "CAP REQ :sasl")
+        self.getRegistrationMessage(2)
+
         self.sendLine(2, "AUTHENTICATE PLAIN")
-        m = self.getMessage(2, filter_pred=lambda m: m.command != "NOTICE")
+        m = self.getMessage(
+            2, filter_pred=lambda m: m.command != "NOTICE", synchronize=False
+        )
         self.assertMessageMatch(
             m,
             command="AUTHENTICATE",
@@ -21,7 +29,9 @@ class AccountTagTestCase(cases.BaseServerTestCase, cases.OptionalityHelper):
             "replied with “AUTHENTICATE +”, but instead sent: {msg}",
         )
         self.sendLine(2, "AUTHENTICATE amlsbGVzAGppbGxlcwBzZXNhbWU=")
-        m = self.getMessage(2, filter_pred=lambda m: m.command != "NOTICE")
+        m = self.getMessage(
+            2, filter_pred=lambda m: m.command != "NOTICE", synchronize=False
+        )
         self.assertMessageMatch(
             m,
             command="900",
diff --git a/irctest/server_tests/test_user_commands.py b/irctest/server_tests/test_user_commands.py
index c913aa4..adac1f7 100644
--- a/irctest/server_tests/test_user_commands.py
+++ b/irctest/server_tests/test_user_commands.py
@@ -121,7 +121,9 @@ class WhoisTestCase(cases.BaseServerTestCase, cases.OptionalityHelper):
 
         <https://defs.ircdocs.horse/defs/numerics.html#rpl-whoisaccount-330>"""
         self.controller.registerUser(self, "shivaram", "sesame")
-        self.connectClient("netcat", account="shivaram", password="sesame")
+        self.connectClient(
+            "netcat", account="shivaram", password="sesame", capabilities=["sasl"]
+        )
         self.getMessages(1)
 
         self.connectClient("curious")
@@ -129,7 +131,7 @@ class WhoisTestCase(cases.BaseServerTestCase, cases.OptionalityHelper):
         messages = self.getMessages(2)
         # 330 RPL_WHOISACCOUNT
         whoisaccount = [message for message in messages if message.command == "330"]
-        self.assertEqual(len(whoisaccount), 1)
+        self.assertEqual(len(whoisaccount), 1, messages)
         params = whoisaccount[0].params
         # <client> <nick> <authname> :<info>
         self.assertEqual(len(params), 4)