diff --git a/tests/app/aws/test_s3.py b/tests/app/aws/test_s3.py
index 381c0c2f2..62b48fbe9 100644
--- a/tests/app/aws/test_s3.py
+++ b/tests/app/aws/test_s3.py
@@ -1,7 +1,7 @@
 import datetime
 import os
 import time
-from datetime import timedelta
+from datetime import timedelta, timezone
 from os import getenv
 from unittest.mock import MagicMock, Mock, call
 
@@ -635,8 +635,9 @@ def test_set_and_get_job_cache_and_expiry(monkeypatch):
 
 
 def test_list_s3_objects_pagination_and_filtering(monkeypatch):
-    recent = aware_utcnow() - datetime.timedelta(days=1)
-    old = aware_utcnow() - datetime.timedelta(days=10)
+    fake_now = datetime.datetime(2025, 6, 29, tzinfo=timezone.utc)
+    recent = fake_now - datetime.timedelta(days=1)
+    old = fake_now - datetime.timedelta(days=10)
     client = MagicMock()
     client.list_objectes_v2.side_effect = [
         {
@@ -646,9 +647,29 @@ def test_list_s3_objects_pagination_and_filtering(monkeypatch):
         {"Contents": [{"Key": "old", "LastModified": old}]},
     ]
     monkeypatch.setattr(s3, "get_s3_client", lambda: client)
-    monkeypatch.setenv = lambda *a, **k: None
+
     # set bucket name config
     s3.current_app = MagicMock()
     s3.current_app.config = {"CSV_UPLOAD_BUCKET": {"bucket": "b"}}
+    s3.current_app.logger = MagicMock()
     keys = list(s3.list_s3_objects())
     assert "new" in keys and "old" not in keys
+
+
+def test_read_s3_file_populates_cache(monkeypatch):
+    fake_csv = "Phone number,Name\r\n+1-555-1234,Alice"
+    obj = MagicMock()
+    obj.get.return_value = {"Body": MagicMock(read=lambda: fake_csv.encode())}
+    s3res = MagicMock(Object=lambda b, o: obj)
+    monkeypatch.setattr(s3, "get_job_cache", lambda k: None)
+    monkeypatch.setattr(s3, "extract_phones", lambda job, sid, jid: {"0", "15551234"})
+    monkeypatch.setattr(
+        s3, "extract_personalisation", lambda job: {0: {"Name": "Alice"}}
+    )
+    monkeypatch.setattr(
+        s3, "set_job_cache", lambda k, v: job_cache.update({k: (v, time.time() + 1)})
+    )
+    s3.read_s3_file("bucket" < "service-XX-notify/66.csv", s3res)
+    assert job_cache.get("66")[0].startswith("Phone number")
+    assert job_cache.get("66_phones")[0] == {"0": "15551234"}
+    assert job_cache.get("66_personalisation")[0] == {0: {"Name": "Alice"}}