diff --git a/mdb/management/commands/dhcp-sync.py b/mdb/management/commands/dhcp-sync.py
deleted file mode 100644
index 3b60a5c..0000000
--- a/mdb/management/commands/dhcp-sync.py
+++ /dev/null
@@ -1,101 +0,0 @@
-import os
-import sys
-from difflib import context_diff
-from django.core.management.base import BaseCommand
-from django.core.mail import mail_admins
-from subprocess import getstatusoutput
-
-from mdb.models import DhcpConfig
-
-
-class Command(BaseCommand):
-    args = '--output <path> [--force] [--restart]'
-    help = 'Generates the DHCP configuration'
-
-    def add_arguments(self, parser):
-        parser.add_argument('--output',
-                            action='store',
-                            dest='output',
-                            default=None,
-                            help='Path to dhcpd.conf, defaults to stdout'),
-        parser.add_argument('--force',
-                            action='store_true',
-                            dest='force',
-                            default=False,
-                            help='Write configuration even if serial is unchanged.'),
-        parser.add_argument('--restart',
-                            action='store_true',
-                            dest='restart',
-                            default=False,
-                            help='Restart dhcp3-server if serial is changed'),
-
-    def handle(self, *args, **options):
-        output = options['output'] if options['output'] else sys.stdout
-        force = options['force']
-        restart = options['restart']
-        restart_command = "/usr/sbin/service isc-dhcp-server restart"
-
-        config = DhcpConfig.objects.filter(name="default").get()
-
-        # do we need to do anything?
-        if config.serial == config.active_serial and not force:
-            print("Nothing to do, serial is the same: %s" % config.serial)
-            sys.exit(0)
-
-        # write to stdout
-        if output == sys.stdout:
-            print(config.dhcpd_configuration())
-            print('Not writing to file, serial not updated')
-            return
-
-        # read current file contents
-        try:
-            with open(output, 'r') as f:
-                old = f.read()
-        except IOError:
-            old = ''
-
-        # write to file
-        new = config.dhcpd_configuration()
-        with open(output, 'w') as f:
-            f.write(new)
-
-        diff = self.calculate_diff(config, new, old)
-
-        print(diff)
-
-        # update serial
-        old_serial = config.active_serial
-        config.active_serial = config.serial
-        config.save()
-
-        # restart the dhcp server?
-        if restart:
-            status, output = getstatusoutput(restart_command)
-            if status != 0:
-                message = (
-                    "Failed to restart dhcp3-server, please inspect...\n\n" +
-                    "%s@%s# %s" % (os.getlogin(), os.uname()[1], restart_command) +
-                    "\n%s\n\n%s" % (output, diff))
-                mail_admins(
-                    subject="FAIL: dhcpd %s -> %s" % (old_serial, config.active_serial),
-                    message=message,
-                    html_message='<pre>%s</pre>' % message)
-                sys.exit(1)
-            else:
-                message = (
-                    "Updated dhcpd configuration to serial %d\n\n" % config.active_serial +
-                    "%s" % diff)
-                mail_admins(
-                    subject="Success: dhcpd %s -> %s" % (old_serial, config.active_serial),
-                    message=message,
-                    html_message='<pre>%s</pre>' % message)
-                sys.exit(0)
-
-    def calculate_diff(self, config, new, old):
-        return "\n".join(context_diff(
-            a=old.splitlines(),
-            b=new.splitlines(),
-            fromfile=str(config.active_serial),
-            tofile=str(config.serial),
-            lineterm=''))
diff --git a/mdb/management/commands/dhcp_sync.py b/mdb/management/commands/dhcp_sync.py
new file mode 100644
index 0000000..517c1b3
--- /dev/null
+++ b/mdb/management/commands/dhcp_sync.py
@@ -0,0 +1,82 @@
+import os
+
+from django.core.management.base import BaseCommand
+
+from mdb.services import discord
+from mdb.services.dhcp_sync import DhcpSyncService
+
+
+class Command(BaseCommand):
+    args = "--output <path> [--force] [--restart]"
+    help = "Generates the DHCP configuration"
+
+    def add_arguments(self, parser):
+        parser.add_argument(
+            "--output",
+            action="store",
+            dest="output",
+            default=None,
+            help="Path to dhcpd.conf, defaults to stdout",
+        )
+        parser.add_argument(
+            "--force",
+            action="store_true",
+            dest="force",
+            default=False,
+            help="Write configuration even if serial is unchanged.",
+        )
+        parser.add_argument(
+            "--restart",
+            action="store_true",
+            dest="restart",
+            default=False,
+            help="Restart isc-dhcp-server if serial is changed",
+        )
+
+    def handle(self, *args, **options):
+        output = options["output"]
+        force = options["force"]
+        restart = options["restart"]
+
+        service = DhcpSyncService(force=force)
+        config = service.get_config()
+
+        if not service.needs_update(config):
+            self.stdout.write("Nothing to do, serial is the same: %s\n" % config.serial)
+            return
+
+        if output is None:
+            self.stdout.write(config.dhcpd_configuration())
+            self.stdout.write("Not writing to file, serial not updated\n")
+            return
+
+        old_serial, diff = service.write_config(config, output)
+        self.stdout.write(diff + "\n")
+
+        if restart:
+            self.restart_and_notify(service, config, old_serial, diff)
+
+    def restart_and_notify(self, service, config, old_serial, diff):
+        self.stdout.write("restarting isc-dhcp-server... ")
+        success, output = service.restart_service()
+
+        if not success:
+            self.stdout.write("fail\n")
+            message = (
+                "Failed to restart isc-dhcp-server, please inspect...\n\n"
+                "%s@%s$ %s\n%s" % (os.getlogin(), os.uname()[1], service.restart_command, output)
+            )
+            discord.notify(
+                subject="⚠️ FAIL: dhcpd %s -> %s" % (old_serial, config.active_serial),
+                message=message,
+                preformatted=diff or None,
+            )
+            raise SystemExit(1)
+
+        self.stdout.write("ok\n")
+        message = "Updated dhcpd configuration to serial %d" % config.active_serial
+        discord.notify(
+            subject="✅ Success: dhcpd %s -> %s" % (old_serial, config.active_serial),
+            message=message,
+            preformatted=diff or None,
+        )
diff --git a/mdb/services/dhcp_sync.py b/mdb/services/dhcp_sync.py
new file mode 100644
index 0000000..78e7303
--- /dev/null
+++ b/mdb/services/dhcp_sync.py
@@ -0,0 +1,59 @@
+from difflib import context_diff
+from subprocess import getstatusoutput
+
+from mdb.models import DhcpConfig
+
+
+class DhcpSyncService:
+    restart_command = "/usr/sbin/service isc-dhcp-server restart"
+
+    def __init__(self, force=False):
+        self.force = force
+
+    def get_config(self):
+        return DhcpConfig.objects.filter(name="default").get()
+
+    def needs_update(self, config):
+        return config.serial != config.active_serial or self.force
+
+    def calculate_diff(self, config, new, old):
+        return "\n".join(
+            context_diff(
+                a=old.splitlines(),
+                b=new.splitlines(),
+                fromfile=str(config.active_serial),
+                tofile=str(config.serial),
+                lineterm="",
+            )
+        )
+
+    def write_config(self, config, output_path):
+        """Write new DHCP config to file and update active_serial.
+
+        Returns (old_serial, diff).
+        """
+        try:
+            with open(output_path, "r") as f:
+                old = f.read()
+        except IOError:
+            old = ""
+
+        new = config.dhcpd_configuration()
+        with open(output_path, "w") as f:
+            f.write(new)
+
+        diff = self.calculate_diff(config, new, old)
+
+        old_serial = config.active_serial
+        config.active_serial = config.serial
+        config.save()
+
+        return old_serial, diff
+
+    def restart_service(self):
+        """Run the DHCP server restart command.
+
+        Returns (success, output).
+        """
+        status, output = getstatusoutput(self.restart_command)
+        return status == 0, output
diff --git a/tests/test_dhcp_sync.py b/tests/test_dhcp_sync.py
new file mode 100644
index 0000000..4b8c382
--- /dev/null
+++ b/tests/test_dhcp_sync.py
@@ -0,0 +1,113 @@
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from mdb.services.dhcp_sync import DhcpSyncService
+
+
+def make_config(serial=2, active_serial=1):
+    config = MagicMock()
+    config.serial = serial
+    config.active_serial = active_serial
+    config.dhcpd_configuration.return_value = "# dhcpd config\nsubnet 10.0.0.0 netmask 255.255.255.0 {}\n"
+    return config
+
+
+@pytest.fixture
+def service():
+    return DhcpSyncService()
+
+
+# --- needs_update ---
+
+def test_needs_update_true_when_serials_differ(service):
+    config = make_config(serial=2, active_serial=1)
+    assert service.needs_update(config) is True
+
+
+def test_needs_update_false_when_serials_match(service):
+    config = make_config(serial=1, active_serial=1)
+    assert service.needs_update(config) is False
+
+
+def test_needs_update_true_when_force_even_if_serials_match():
+    svc = DhcpSyncService(force=True)
+    config = make_config(serial=1, active_serial=1)
+    assert svc.needs_update(config) is True
+
+
+# --- calculate_diff ---
+
+def test_calculate_diff_identical_returns_empty(service):
+    config = make_config()
+    assert service.calculate_diff(config, "line\n", "line\n") == ""
+
+
+def test_calculate_diff_format(service):
+    config = make_config(serial=2, active_serial=1)
+    diff = service.calculate_diff(config, "new line\n", "old line\n")
+    assert "*** 1" in diff
+    assert "--- 2" in diff
+    assert "! old line" in diff
+    assert "! new line" in diff
+
+
+# --- write_config ---
+
+def test_write_config_creates_file_with_config_contents(service, tmp_path):
+    config = make_config()
+    output_path = str(tmp_path / "dhcpd.conf")
+
+    service.write_config(config, output_path)
+
+    with open(output_path) as f:
+        assert f.read() == config.dhcpd_configuration.return_value
+
+
+def test_write_config_updates_active_serial(service, tmp_path):
+    config = make_config(serial=5, active_serial=3)
+    output_path = str(tmp_path / "dhcpd.conf")
+
+    service.write_config(config, output_path)
+
+    assert config.active_serial == 5
+    config.save.assert_called_once()
+
+
+def test_write_config_returns_old_serial(service, tmp_path):
+    config = make_config(serial=2, active_serial=1)
+    output_path = str(tmp_path / "dhcpd.conf")
+
+    old_serial, diff = service.write_config(config, output_path)
+
+    assert old_serial == 1
+
+
+def test_write_config_diff_reflects_changes(service, tmp_path):
+    output_path = str(tmp_path / "dhcpd.conf")
+    with open(output_path, "w") as f:
+        f.write("old content\n")
+
+    config = make_config(serial=2, active_serial=1)
+    config.dhcpd_configuration.return_value = "new content\n"
+
+    old_serial, diff = service.write_config(config, output_path)
+
+    assert "old content" in diff
+    assert "new content" in diff
+
+
+# --- restart_service ---
+
+def test_restart_service_returns_true_on_success(service):
+    with patch("mdb.services.dhcp_sync.getstatusoutput", return_value=(0, "")):
+        success, output = service.restart_service()
+    assert success is True
+    assert output == ""
+
+
+def test_restart_service_returns_false_on_failure(service):
+    with patch("mdb.services.dhcp_sync.getstatusoutput", return_value=(1, "Job failed")):
+        success, output = service.restart_service()
+    assert success is False
+    assert output == "Job failed"
diff --git a/tests/test_dhcp_sync_command.py b/tests/test_dhcp_sync_command.py
new file mode 100644
index 0000000..89c5443
--- /dev/null
+++ b/tests/test_dhcp_sync_command.py
@@ -0,0 +1,131 @@
+from io import StringIO
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from mdb.management.commands.dhcp_sync import Command as CommandClass
+
+
+@pytest.fixture
+def cmd():
+    c = CommandClass()
+    c.stdout = StringIO()
+    c.stderr = StringIO()
+    return c
+
+
+def make_service(serial=2, active_serial=1, restart_success=True, restart_output=""):
+    svc = MagicMock()
+    svc.force = False
+    svc.restart_command = "/usr/sbin/service isc-dhcp-server restart"
+    config = MagicMock()
+    config.serial = serial
+    config.active_serial = active_serial
+    config.dhcpd_configuration.return_value = "# dhcpd config\n"
+    svc.get_config.return_value = config
+    svc.needs_update.return_value = serial != active_serial
+    svc.write_config.return_value = (active_serial, "- old\n+ new")
+    svc.restart_service.return_value = (restart_success, restart_output)
+    return svc, config
+
+
+# --- handle: nothing to do ---
+
+def test_handle_prints_nothing_to_do_when_no_update_needed(cmd):
+    svc, config = make_service(serial=1, active_serial=1)
+    svc.needs_update.return_value = False
+    with patch("mdb.management.commands.dhcp_sync.DhcpSyncService", return_value=svc):
+        cmd.handle(output=None, force=False, restart=False)
+    assert "Nothing to do" in cmd.stdout.getvalue()
+
+
+# --- handle: stdout mode ---
+
+def test_handle_prints_config_to_stdout_when_no_output_path(cmd):
+    svc, config = make_service()
+    with patch("mdb.management.commands.dhcp_sync.DhcpSyncService", return_value=svc):
+        cmd.handle(output=None, force=False, restart=False)
+    assert "# dhcpd config" in cmd.stdout.getvalue()
+    assert "Not writing to file" in cmd.stdout.getvalue()
+
+
+def test_handle_does_not_write_file_when_no_output_path(cmd):
+    svc, config = make_service()
+    with patch("mdb.management.commands.dhcp_sync.DhcpSyncService", return_value=svc):
+        cmd.handle(output=None, force=False, restart=False)
+    svc.write_config.assert_not_called()
+
+
+# --- handle: file mode ---
+
+def test_handle_calls_write_config_when_output_given(cmd, tmp_path):
+    svc, config = make_service()
+    output_path = str(tmp_path / "dhcpd.conf")
+    with patch("mdb.management.commands.dhcp_sync.DhcpSyncService", return_value=svc):
+        cmd.handle(output=output_path, force=False, restart=False)
+    svc.write_config.assert_called_once_with(config, output_path)
+
+
+def test_handle_does_not_restart_when_restart_false(cmd, tmp_path):
+    svc, config = make_service()
+    output_path = str(tmp_path / "dhcpd.conf")
+    with patch("mdb.management.commands.dhcp_sync.DhcpSyncService", return_value=svc):
+        with patch.object(cmd, "restart_and_notify") as mock_restart:
+            cmd.handle(output=output_path, force=False, restart=False)
+    mock_restart.assert_not_called()
+
+
+def test_handle_calls_restart_and_notify_when_restart_true(cmd, tmp_path):
+    svc, config = make_service()
+    output_path = str(tmp_path / "dhcpd.conf")
+    with patch("mdb.management.commands.dhcp_sync.DhcpSyncService", return_value=svc):
+        with patch.object(cmd, "restart_and_notify") as mock_restart:
+            cmd.handle(output=output_path, force=False, restart=True)
+    mock_restart.assert_called_once()
+
+
+# --- restart_and_notify ---
+
+def test_restart_and_notify_success_writes_ok(cmd):
+    svc, config = make_service(restart_success=True)
+    with patch("mdb.management.commands.dhcp_sync.discord"):
+        cmd.restart_and_notify(svc, config, old_serial=1, diff="- old\n+ new")
+    assert "ok" in cmd.stdout.getvalue()
+
+
+def test_restart_and_notify_success_calls_discord(cmd):
+    svc, config = make_service(restart_success=True)
+    with patch("mdb.management.commands.dhcp_sync.discord") as mock_discord:
+        cmd.restart_and_notify(svc, config, old_serial=1, diff="- old\n+ new")
+    mock_discord.notify.assert_called_once()
+    assert "✅" in mock_discord.notify.call_args.kwargs["subject"]
+
+
+def test_restart_and_notify_success_passes_diff_as_preformatted(cmd):
+    svc, config = make_service(restart_success=True)
+    with patch("mdb.management.commands.dhcp_sync.discord") as mock_discord:
+        cmd.restart_and_notify(svc, config, old_serial=1, diff="- old\n+ new")
+    assert mock_discord.notify.call_args.kwargs["preformatted"] == "- old\n+ new"
+
+
+def test_restart_and_notify_failure_writes_fail_and_exits(cmd):
+    svc, config = make_service(restart_success=False, restart_output="Job failed")
+    with patch("mdb.management.commands.dhcp_sync.discord"):
+        with patch("os.getlogin", return_value="testuser"):
+            with pytest.raises(SystemExit) as exc:
+                cmd.restart_and_notify(svc, config, old_serial=1, diff="")
+    assert exc.value.code == 1
+    assert "fail" in cmd.stdout.getvalue()
+
+
+def test_restart_and_notify_failure_discord_includes_command_and_output(cmd):
+    svc, config = make_service(restart_success=False, restart_output="Job failed")
+    with patch("mdb.management.commands.dhcp_sync.discord") as mock_discord:
+        with patch("os.getlogin", return_value="testuser"):
+            with pytest.raises(SystemExit):
+                cmd.restart_and_notify(svc, config, old_serial=1, diff="")
+    subject = mock_discord.notify.call_args.kwargs["subject"]
+    message = mock_discord.notify.call_args.kwargs["message"]
+    assert "⚠️" in subject
+    assert "isc-dhcp-server" in message
+    assert "Job failed" in message