diff --git a/com/tests/test_api.py b/com/tests/test_api.py
index 0a8f3f96..cfc0e35f 100644
--- a/com/tests/test_api.py
+++ b/com/tests/test_api.py
@@ -1,11 +1,15 @@
 from dataclasses import dataclass
+from datetime import datetime, timedelta
 from pathlib import Path
+from typing import Callable
 from unittest.mock import MagicMock, patch
 
 import pytest
 from django.conf import settings
+from django.http import HttpResponse
 from django.test.client import Client
 from django.urls import reverse
+from django.utils import timezone
 
 from com.calendar import IcsCalendar
 
@@ -20,13 +24,29 @@ class MockResponse:
         return self.value.encode("utf8")
 
 
+def accel_redirect_to_file(response: HttpResponse) -> Path | None:
+    redirect = Path(response.headers.get("X-Accel-Redirect", ""))
+    if not redirect.is_relative_to(Path("/") / settings.MEDIA_ROOT.stem):
+        return None
+    return settings.MEDIA_ROOT / redirect.relative_to(
+        Path("/") / settings.MEDIA_ROOT.stem
+    )
+
+
 @pytest.mark.django_db
 class TestExternalCalendar:
     @pytest.fixture
     def mock_request(self):
-        request = MagicMock()
-        with patch("urllib3.request", request):
-            yield request
+        mock = MagicMock()
+        with patch("urllib3.request", mock):
+            yield mock
+
+    @pytest.fixture
+    def mock_current_time(self):
+        mock = MagicMock()
+        original = timezone.now
+        with patch("django.utils.timezone.now", mock):
+            yield mock, original
 
     @pytest.fixture(autouse=True)
     def clear_cache(self):
@@ -44,11 +64,45 @@ class TestExternalCalendar:
         mock_request.return_value = external_response
         response = client.get(reverse("api:calendar_external"))
         assert response.status_code == 200
-        redirect = Path(response.headers.get("X-Accel-Redirect", ""))
-        assert redirect.is_relative_to(Path("/") / settings.MEDIA_ROOT.stem)
-        out_file = settings.MEDIA_ROOT / redirect.relative_to(
-            Path("/") / settings.MEDIA_ROOT.stem
-        )
+        out_file = accel_redirect_to_file(response)
+        assert out_file is not None
         assert out_file.exists()
         with open(out_file, "r") as f:
             assert f.read() == external_response.value
+
+    def test_fetch_caching(
+        self,
+        client: Client,
+        mock_request: MagicMock,
+        mock_current_time: tuple[MagicMock, Callable[[], datetime]],
+    ):
+        fake_current_time, original_timezone = mock_current_time
+        start_time = original_timezone()
+
+        fake_current_time.return_value = start_time
+        external_response = MockResponse(200, "Definitely an ICS")
+        mock_request.return_value = external_response
+
+        with open(
+            accel_redirect_to_file(client.get(reverse("api:calendar_external"))), "r"
+        ) as f:
+            assert f.read() == external_response.value
+
+        mock_request.return_value = MockResponse(200, "This should be ignored")
+        with open(
+            accel_redirect_to_file(client.get(reverse("api:calendar_external"))), "r"
+        ) as f:
+            assert f.read() == external_response.value
+
+        mock_request.assert_called_once()
+
+        fake_current_time.return_value = start_time + timedelta(hours=1, seconds=1)
+        external_response = MockResponse(200, "This won't be ignored")
+        mock_request.return_value = external_response
+
+        with open(
+            accel_redirect_to_file(client.get(reverse("api:calendar_external"))), "r"
+        ) as f:
+            assert f.read() == external_response.value
+
+        assert mock_request.call_count == 2