diff --git a/bin/tests/system/chain/ans4/ans.py b/bin/tests/system/chain/ans4/ans.py
index 3e042ea58c..249da49b9a 100755
--- a/bin/tests/system/chain/ans4/ans.py
+++ b/bin/tests/system/chain/ans4/ans.py
@@ -473,7 +473,8 @@ class ChainResponseHandler(DomainHandler):
 
 
 def main() -> None:
-    server = ControllableAsyncDnsServer(commands=[ChainSetupCommand])
+    server = ControllableAsyncDnsServer()
+    server.install_control_command(ChainSetupCommand())
     server.run()
 
 
diff --git a/bin/tests/system/fetchlimit/ans4/ans.py b/bin/tests/system/fetchlimit/ans4/ans.py
index 34891fa310..52be94125c 100644
--- a/bin/tests/system/fetchlimit/ans4/ans.py
+++ b/bin/tests/system/fetchlimit/ans4/ans.py
@@ -39,7 +39,8 @@ class MaybeDelayedAddressAnswerHandler(ResponseHandler):
 
 
 def main() -> None:
-    server = ControllableAsyncDnsServer([ToggleResponsesCommand])
+    server = ControllableAsyncDnsServer()
+    server.install_control_command(ToggleResponsesCommand())
     server.install_response_handler(MaybeDelayedAddressAnswerHandler())
     server.run()
 
diff --git a/bin/tests/system/forward/ans11/ans.py b/bin/tests/system/forward/ans11/ans.py
index 8d0b3e9b33..0b4ec5682e 100644
--- a/bin/tests/system/forward/ans11/ans.py
+++ b/bin/tests/system/forward/ans11/ans.py
@@ -49,7 +49,8 @@ class ExtraAnswersHandler(DomainHandler):
 
 
 def main() -> None:
-    server = ControllableAsyncDnsServer(commands=[ToggleResponsesCommand])
+    server = ControllableAsyncDnsServer()
+    server.install_control_command(ToggleResponsesCommand())
     server.install_response_handler(ExtraAnswersHandler())
     server.run()
 
diff --git a/bin/tests/system/forward/ans6/ans.py b/bin/tests/system/forward/ans6/ans.py
index f63cdcd4d5..a9fd0b8ac6 100644
--- a/bin/tests/system/forward/ans6/ans.py
+++ b/bin/tests/system/forward/ans6/ans.py
@@ -72,7 +72,8 @@ class ChaseDsHandler(ResponseHandler):
 
 
 def main() -> None:
-    server = ControllableAsyncDnsServer([ToggleResponsesCommand])
+    server = ControllableAsyncDnsServer()
+    server.install_control_command(ToggleResponsesCommand())
     server.install_response_handler(ChaseDsHandler())
     server.run()
 
diff --git a/bin/tests/system/isctest/asyncserver.py b/bin/tests/system/isctest/asyncserver.py
index c91f63a123..27a981446b 100644
--- a/bin/tests/system/isctest/asyncserver.py
+++ b/bin/tests/system/isctest/asyncserver.py
@@ -21,7 +21,6 @@ from typing import (
     List,
     Optional,
     Tuple,
-    Type,
     Union,
     cast,
 )
@@ -1281,22 +1280,29 @@ class ControllableAsyncDnsServer(AsyncDnsServer):
 
     _CONTROL_DOMAIN = "_control."
 
-    def __init__(self, commands: List[Type["ControlCommand"]]):
-        super().__init__()
-        self._control_domain = dns.name.from_text(self._CONTROL_DOMAIN)
-        self._commands: Dict[dns.name.Name, "ControlCommand"] = {}
-        for command_class in commands:
-            command = command_class()
-            command_subdomain = dns.name.Name([command.control_subdomain])
-            control_subdomain = command_subdomain.concatenate(self._control_domain)
-            try:
-                existing_command = self._commands[control_subdomain]
-            except KeyError:
-                self._commands[control_subdomain] = command
-            else:
-                raise RuntimeError(
-                    f"{control_subdomain} already handled by {existing_command}"
-                )
+    @functools.cached_property
+    def _control_domain(self) -> dns.name.Name:
+        return dns.name.from_text(self._CONTROL_DOMAIN)
+
+    @functools.cached_property
+    def _commands(self) -> Dict[dns.name.Name, "ControlCommand"]:
+        return {}
+
+    def install_control_commands(self, commands: List["ControlCommand"]) -> None:
+        for command in commands:
+            self.install_control_command(command)
+
+    def install_control_command(self, command: "ControlCommand") -> None:
+        command_subdomain = dns.name.Name([command.control_subdomain])
+        control_subdomain = command_subdomain.concatenate(self._control_domain)
+        try:
+            existing_command = self._commands[control_subdomain]
+        except KeyError:
+            self._commands[control_subdomain] = command
+        else:
+            raise RuntimeError(
+                f"{control_subdomain} already handled by {existing_command}"
+            )
 
     async def _prepare_responses(
         self, qctx: QueryContext
diff --git a/bin/tests/system/xfer/ans9/ans.py b/bin/tests/system/xfer/ans9/ans.py
index 56c80becb9..f1a4bf5437 100644
--- a/bin/tests/system/xfer/ans9/ans.py
+++ b/bin/tests/system/xfer/ans9/ans.py
@@ -106,6 +106,7 @@ class AXFRServer(DomainHandler):
 
 
 if __name__ == "__main__":
-    server = ControllableAsyncDnsServer([ToggleResponsesCommand])
+    server = ControllableAsyncDnsServer()
+    server.install_control_command(ToggleResponsesCommand())
     server.install_response_handler(AXFRServer())
     server.run()