From ff4ad07a2b719147a96530d6f1ad893230425831 Mon Sep 17 00:00:00 2001
From: Jun-te Kim <juntekim@googlemail.com>
Date: Wed, 13 May 2026 11:41:21 +0000
Subject: [PATCH] retry

---
 backend/epc_client/tests/test_client.py | 86 ++++++++++++++++++++++++-
 1 file changed, 85 insertions(+), 1 deletion(-)

diff --git a/backend/epc_client/tests/test_client.py b/backend/epc_client/tests/test_client.py
index 0e95a844..70425a92 100644
--- a/backend/epc_client/tests/test_client.py
+++ b/backend/epc_client/tests/test_client.py
@@ -8,12 +8,13 @@ from datatypes.epc.domain.epc_property_data import EpcPropertyData
 from backend.epc_client.tests.conftest import make_search_row
 
 
-def _mock_response(status_code=200, json_data=None):
+def _mock_response(status_code=200, json_data=None, headers=None):
     resp = MagicMock()
     resp.status_code = status_code
     resp.is_success = 200 <= status_code < 300
     resp.json.return_value = json_data or {}
     resp.text = str(json_data)
+    resp.headers = headers or {}
     return resp
 
 
@@ -63,6 +64,89 @@ def test_get_by_certificate_number_retries_on_429_and_succeeds(
     assert isinstance(result, EpcPropertyData)
 
 
+# ---------------------------------------------------------------------------
+# Test 3b: 429 with Retry-After header → sleeps for that value
+# ---------------------------------------------------------------------------
+
+
+def test_429_retry_after_header_drives_sleep_duration(
+    epc_service, rdsap_21_0_1_cert
+):
+    cert_response = {"data": rdsap_21_0_1_cert}
+    responses = [
+        _mock_response(429, headers={"Retry-After": "7"}),
+        _mock_response(200, cert_response),
+    ]
+    with patch("httpx.get", side_effect=responses), patch(
+        "backend.epc_client._retry.time.sleep"
+    ) as mock_sleep:
+        epc_service.get_by_certificate_number("CERT-001")
+
+    mock_sleep.assert_called_once_with(7.0)
+
+
+# ---------------------------------------------------------------------------
+# Test 3c: 429 without Retry-After → falls back to exponential backoff
+# ---------------------------------------------------------------------------
+
+
+def test_429_without_retry_after_uses_exponential_backoff(
+    epc_service, rdsap_21_0_1_cert
+):
+    cert_response = {"data": rdsap_21_0_1_cert}
+    responses = [
+        _mock_response(429),
+        _mock_response(429),
+        _mock_response(200, cert_response),
+    ]
+    with patch("httpx.get", side_effect=responses), patch(
+        "backend.epc_client._retry.time.sleep"
+    ) as mock_sleep:
+        epc_service.get_by_certificate_number("CERT-001")
+
+    assert mock_sleep.call_args_list == [call(1.0), call(2.0)]
+
+
+# ---------------------------------------------------------------------------
+# Test 3d: malformed Retry-After header → falls back to exponential backoff
+# ---------------------------------------------------------------------------
+
+
+def test_429_malformed_retry_after_falls_back_to_backoff(
+    epc_service, rdsap_21_0_1_cert
+):
+    cert_response = {"data": rdsap_21_0_1_cert}
+    responses = [
+        _mock_response(429, headers={"Retry-After": "Wed, 21 Oct 2026 07:28:00 GMT"}),
+        _mock_response(200, cert_response),
+    ]
+    with patch("httpx.get", side_effect=responses), patch(
+        "backend.epc_client._retry.time.sleep"
+    ) as mock_sleep:
+        epc_service.get_by_certificate_number("CERT-001")
+
+    mock_sleep.assert_called_once_with(1.0)
+
+
+# ---------------------------------------------------------------------------
+# Test 3e: Retry-After capped by max_backoff to avoid hostile/buggy values
+# ---------------------------------------------------------------------------
+
+
+def test_429_retry_after_capped_by_max_backoff(epc_service, rdsap_21_0_1_cert):
+    cert_response = {"data": rdsap_21_0_1_cert}
+    responses = [
+        _mock_response(429, headers={"Retry-After": "9999"}),
+        _mock_response(200, cert_response),
+    ]
+    with patch("httpx.get", side_effect=responses), patch(
+        "backend.epc_client._retry.time.sleep"
+    ) as mock_sleep:
+        epc_service.get_by_certificate_number("CERT-001")
+
+    mock_sleep.assert_called_once_with(60.0)
+
+
 # ---------------------------------------------------------------------------
 # Test 4: get_by_uprn empty search → None
 # ---------------------------------------------------------------------------