diff --git a/zerver/lib/zcommand.py b/zerver/lib/zcommand.py
new file mode 100644
index 0000000000..8d198ffaa4
--- /dev/null
+++ b/zerver/lib/zcommand.py
@@ -0,0 +1,32 @@
+from typing import Any, Dict
+from django.utils.translation import ugettext as _
+
+from zerver.models import UserProfile
+from zerver.lib.actions import do_set_user_display_setting
+from zerver.lib.exceptions import JsonableError
+
+def process_zcommands(command: str, user_profile: UserProfile) -> Dict[str, Any]:
+
+    if command == 'ping':
+        ret = dict()  # type: Dict[str, Any]
+        return ret
+
+    if command == 'night':
+        if user_profile.night_mode:
+            msg = 'You are still in night mode.'
+        else:
+            msg = 'Changed to night mode! To revert night mode, type `/day`.'
+            do_set_user_display_setting(user_profile, 'night_mode', True)
+        ret = dict(msg=msg)
+        return ret
+
+    if command == 'day':
+        if user_profile.night_mode:
+            msg = 'Changed to day mode! To revert day mode, type `/night`.'
+            do_set_user_display_setting(user_profile, 'night_mode', False)
+        else:
+            msg = 'You are still in day mode.'
+        ret = dict(msg=msg)
+        return ret
+
+    raise JsonableError(_('No such command: %s') % (command,))
diff --git a/zerver/tests/test_messages.py b/zerver/tests/test_messages.py
index e46a1af70c..4f9db2f148 100644
--- a/zerver/tests/test_messages.py
+++ b/zerver/tests/test_messages.py
@@ -999,39 +999,6 @@ class SewMessageAndReactionTest(ZulipTestCase):
 
 class MessagePOSTTest(ZulipTestCase):
 
-    def test_zcommand(self) -> None:
-        self.login(self.example_email("hamlet"))
-
-        payload = dict(command="boil-ocean")
-        result = self.client_post("/json/zcommand", payload)
-        self.assert_json_error(result, "No such command: boil-ocean")
-
-        payload = dict(command="ping")
-        result = self.client_post("/json/zcommand", payload)
-        self.assert_json_success(result)
-
-        user = self.example_user('hamlet')
-        user.night_mode = False
-        user.save()
-
-        payload = dict(command="night")
-        result = self.client_post("/json/zcommand", payload)
-        self.assert_json_success(result)
-        self.assertIn('Changed to night', result.json()['msg'])
-
-        result = self.client_post("/json/zcommand", payload)
-        self.assert_json_success(result)
-        self.assertIn('still in night mode', result.json()['msg'])
-
-        payload = dict(command="day")
-        result = self.client_post("/json/zcommand", payload)
-        self.assert_json_success(result)
-        self.assertIn('Changed to day', result.json()['msg'])
-
-        result = self.client_post("/json/zcommand", payload)
-        self.assert_json_success(result)
-        self.assertIn('still in day mode', result.json()['msg'])
-
     def test_message_to_self(self) -> None:
         """
         Sending a message to a stream to which you are subscribed is
diff --git a/zerver/tests/test_zcommand.py b/zerver/tests/test_zcommand.py
new file mode 100644
index 0000000000..3007fff91c
--- /dev/null
+++ b/zerver/tests/test_zcommand.py
@@ -0,0 +1,51 @@
+# -*- coding: utf-8 -*-
+
+from zerver.lib.test_classes import (
+    ZulipTestCase,
+)
+
+class ZcommandTest(ZulipTestCase):
+
+    def test_invalid_zcommand(self) -> None:
+        self.login(self.example_email("hamlet"))
+
+        payload = dict(command="boil-ocean")
+        result = self.client_post("/json/zcommand", payload)
+        self.assert_json_error(result, "No such command: boil-ocean")
+
+    def test_ping_zcommand(self) -> None:
+        self.login(self.example_email("hamlet"))
+
+        payload = dict(command="ping")
+        result = self.client_post("/json/zcommand", payload)
+        self.assert_json_success(result)
+
+    def test_night_zcommand(self) -> None:
+        self.login(self.example_email("hamlet"))
+        user = self.example_user('hamlet')
+        user.night_mode = False
+        user.save()
+
+        payload = dict(command="night")
+        result = self.client_post("/json/zcommand", payload)
+        self.assert_json_success(result)
+        self.assertIn('Changed to night', result.json()['msg'])
+
+        result = self.client_post("/json/zcommand", payload)
+        self.assert_json_success(result)
+        self.assertIn('still in night mode', result.json()['msg'])
+
+    def test_day_zcommand(self) -> None:
+        self.login(self.example_email("hamlet"))
+        user = self.example_user('hamlet')
+        user.night_mode = True
+        user.save()
+
+        payload = dict(command="day")
+        result = self.client_post("/json/zcommand", payload)
+        self.assert_json_success(result)
+        self.assertIn('Changed to day', result.json()['msg'])
+
+        result = self.client_post("/json/zcommand", payload)
+        self.assert_json_success(result)
+        self.assertIn('still in day mode', result.json()['msg'])
diff --git a/zerver/views/messages.py b/zerver/views/messages.py
index c6752a4f31..a1a8f1df2a 100644
--- a/zerver/views/messages.py
+++ b/zerver/views/messages.py
@@ -13,12 +13,12 @@ from zerver.decorator import has_request_variables, \
     REQ, to_non_negative_int
 from django.utils.html import escape as escape_html
 from zerver.lib import bugdown
+from zerver.lib.zcommand import process_zcommands
 from zerver.lib.actions import recipient_for_emails, do_update_message_flags, \
     compute_mit_user_fullname, compute_irc_user_fullname, compute_jabber_user_fullname, \
     create_mirror_user_if_needed, check_send_message, do_update_message, \
     extract_recipients, truncate_body, render_incoming_message, do_delete_message, \
     do_mark_all_as_read, do_mark_stream_messages_as_read, \
-    do_set_user_display_setting, \
     get_user_info_for_message_updates, check_schedule_message
 from zerver.lib.queue import queue_json_publish
 from zerver.lib.message import (
@@ -684,29 +684,7 @@ def find_first_unread_anchor(sa_conn: Any,
 @has_request_variables
 def zcommand_backend(request: HttpRequest, user_profile: UserProfile,
                      command: str=REQ('command')) -> HttpResponse:
-    if command == 'ping':
-        ret = dict()  # type: Dict[str, Any]
-        return json_success(ret)
-
-    if command == 'night':
-        if user_profile.night_mode:
-            msg = 'You are still in night mode.'
-        else:
-            msg = 'Changed to night mode! To revert night mode, type `/day`.'
-            do_set_user_display_setting(user_profile, 'night_mode', True)
-        ret = dict(msg=msg)
-        return json_success(ret)
-
-    if command == 'day':
-        if user_profile.night_mode:
-            msg = 'Changed to day mode! To revert day mode, type `/night`.'
-            do_set_user_display_setting(user_profile, 'night_mode', False)
-        else:
-            msg = 'You are still in day mode.'
-        ret = dict(msg=msg)
-        return json_success(ret)
-
-    raise JsonableError(_('No such command: %s') % (command,))
+    return json_success(process_zcommands(command, user_profile))
 
 @has_request_variables
 def get_messages_backend(request: HttpRequest, user_profile: UserProfile,