test(pricemon): pin telegram notification contract

Add integration tests covering the price-drop → Telegram alert flow:

- Sends Telegram MarkdownV2 message to global SiteSettings chat_id when
  detected price <= watcher.alert_price_threshold.
- No alert when global creds missing.
- No alert when price above threshold.
- No alert when threshold unset on watcher.
- Non-recurring watcher with an undismissed alert is not re-notified.
- Telegram API failure does not break the check (snapshot + alert row
  still persist, last_price updates).

tests/test_pricemon.py

@@ -1,8 +1,10 @@
+from decimal import Decimal
 from unittest.mock import patch
 
 import pytest
 from django.urls import reverse
 
+from links.models import SiteSettings
 from pricemon.models import PriceAlert, PriceWatcher
 
 
@@ -26,6 +28,23 @@ def alert(watcher):
     )
 
 
+@pytest.fixture
+def telegram_creds():
+    ss = SiteSettings.get()
+    ss.telegram_bot_token = '123:abc'
+    ss.telegram_chat_id = '999'
+    ss.save()
+    return ss
+
+
+@pytest.fixture
+def threshold_watcher(watcher):
+    watcher.alert_price_threshold = Decimal('100.00')
+    watcher.last_price = Decimal('120.00')
+    watcher.save()
+    return watcher
+
+
 @pytest.mark.django_db
 class TestPriceMonitorToggle:
     def test_dashboard_shows_disable_action_for_enabled_watcher(self, client, watcher):
@@ -83,3 +102,114 @@ class TestPriceMonitorAlertsPartial:
         assert 'alert-{}'.format(alert.pk) in body
         assert 'View' in body and 'Dismiss' in body
         assert reverse('pricemon-dismiss-alert', args=[alert.pk]) in body
+
+
+@pytest.mark.django_db
+class TestPriceMonitorTelegram:
+    def _check(self, watcher_pk):
+        with patch('pricemon.scraper.fetch_price') as fetch, patch(
+            'pricemon.notifications.requests.post'
+        ) as post:
+            fetch.return_value = (Decimal('90.00'), '$90', '')
+            post.return_value.status_code = 200
+            post.return_value.raise_for_status.return_value = None
+            from pricemon.tasks import check_watcher
+
+            check_watcher(watcher_pk)
+        return post
+
+    def test_sends_telegram_when_price_meets_threshold(self, threshold_watcher, telegram_creds):
+        post = self._check(threshold_watcher.pk)
+
+        post.assert_called_once()
+        url = post.call_args[0][0]
+        assert url.endswith(f'/bot{telegram_creds.telegram_bot_token}/sendMessage')
+        body = post.call_args.kwargs['json']
+        assert body['chat_id'] == '999'
+        assert body['parse_mode'] == 'MarkdownV2'
+        assert 'Price Drop Alert' in body['text']
+        assert threshold_watcher.name in body['text']
+        assert PriceAlert.objects.count() == 1
+
+    def test_no_telegram_without_global_creds(self, threshold_watcher):
+        SiteSettings.get().delete()
+        with patch('pricemon.scraper.fetch_price') as fetch, patch(
+            'pricemon.notifications.requests.post'
+        ) as post:
+            fetch.return_value = (Decimal('90.00'), '$90', '')
+            post.return_value.status_code = 200
+            post.return_value.raise_for_status.return_value = None
+            from pricemon.tasks import check_watcher
+
+            check_watcher(threshold_watcher.pk)
+
+        post.assert_not_called()
+        assert PriceAlert.objects.count() == 1
+
+    def test_no_alert_when_price_above_threshold(self, threshold_watcher, telegram_creds):
+        with patch('pricemon.scraper.fetch_price') as fetch, patch(
+            'pricemon.notifications.requests.post'
+        ) as post:
+            fetch.return_value = (Decimal('110.00'), '$110', '')
+            post.return_value.status_code = 200
+            post.return_value.raise_for_status.return_value = None
+            from pricemon.tasks import check_watcher
+
+            check_watcher(threshold_watcher.pk)
+
+        post.assert_not_called()
+        assert PriceAlert.objects.count() == 0
+
+    def test_no_alert_when_threshold_unset(self, watcher, telegram_creds):
+        with patch('pricemon.scraper.fetch_price') as fetch, patch(
+            'pricemon.notifications.requests.post'
+        ) as post:
+            fetch.return_value = (Decimal('1.00'), '$1', '')
+            post.return_value.status_code = 200
+            post.return_value.raise_for_status.return_value = None
+            from pricemon.tasks import check_watcher
+
+            check_watcher(watcher.pk)
+
+        post.assert_not_called()
+        assert PriceAlert.objects.count() == 0
+
+    def test_non_recurring_alert_skipped_if_undismissed(
+        self, threshold_watcher, telegram_creds
+    ):
+        threshold_watcher.recurring_notification = False
+        threshold_watcher.save()
+        PriceAlert.objects.create(
+            watcher=threshold_watcher,
+            old_price='120.00',
+            new_price='95.00',
+            drop_pct='20.83',
+            dismissed=False,
+        )
+        with patch('pricemon.scraper.fetch_price') as fetch, patch(
+            'pricemon.notifications.requests.post'
+        ) as post:
+            fetch.return_value = (Decimal('90.00'), '$90', '')
+            post.return_value.status_code = 200
+            post.return_value.raise_for_status.return_value = None
+            from pricemon.tasks import check_watcher
+
+            check_watcher(threshold_watcher.pk)
+
+        post.assert_not_called()
+        assert PriceAlert.objects.count() == 1
+
+    def test_telegram_failure_does_not_break_check(self, threshold_watcher, telegram_creds):
+        with patch('pricemon.scraper.fetch_price') as fetch, patch(
+            'pricemon.notifications.requests.post'
+        ) as post:
+            fetch.return_value = (Decimal('90.00'), '$90', '')
+            post.side_effect = Exception('Boom from Telegram')
+            from pricemon.tasks import check_watcher
+
+            check_watcher(threshold_watcher.pk)
+
+        post.assert_called_once()
+        assert PriceAlert.objects.count() == 1
+        threshold_watcher.refresh_from_db()
+        assert threshold_watcher.last_price == Decimal('90.00')